Woven intravascular devices and methods for making the same

ABSTRACT

Self-expandable, woven intravascular devices for use as stents (both straight and tapered), filters (both temporary and permanent) and occluders for insertion and implantation into a variety of anatomical structures. The devices may be formed from shape memory metals such as nitinol. The devices may also be formed from biodegradable materials. Delivery systems for the devices include two hollow tubes that operate coaxially. A device is secured to the tubes prior to the implantation and delivery of the device by securing one end of the device to the outside of the inner tube and by securing the other end of the device to the outside of the outer tube. The stents may be partially or completely covered by graft materials, but may also be bare. The devices may be formed from a single wire. The devices may be formed by either hand or machine weaving. The devices may be created by bending shape memory wires around tabs projecting from a template, and weaving the ends of the wires to create the body of the device such that the wires cross each other to form a plurality of angles, at least one of the angles being obtuse. The value of the obtuse angle may be increased by axially compressing the body.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 10/244,245, filed Sep. 16, 2002, which is a divisionalapplication of U.S. patent application Ser. No. 09/496,243, filed Feb.1, 2000, now U.S. Pat. No. 7,018,401, which claims priority benefitunder 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No.60/118,211 filed Feb. 1, 1999 and U.S. Provisional Patent ApplicationSer. No. 60/125,191 filed Mar. 18, 1999. The entire texts of theabove-referenced disclosures are specifically incorporated by referenceherein without disclaimer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to intravascular devices. Moreparticularly, it concerns self-expandable woven intravascular devicesfor use as stents, occluders or filters, the methods of making the same,and the apparatus and methods for delivery of the same into a livingcreature.

2. Description of Related Art

Intravascular devices that serve as stents or filters constructed usinga plain weave, such as the stent disclosed in U.S. Pat. No. 4,655,771 toWallsten (hereinafter, the WALLSTENT), have a propensity to show ahigh-degree of elongation axially with diameter reduction. This isespecially significant, when the angle of the crossing wires is close tothe largest possible. The closer that the angle between the wires is to180°, the more the corresponding elongation of the stent is at a givenpercentage of decrease in diameter. Any discrepancy between thediameters of the stent and the vessel can result in a considerableelongation of the stent. Simultaneously, the woven type stent has thelargest expansile force and hence the biggest resistance to outercompression when the angle between the crossing wires is close to 180°.In some applications, such as outer compression by a space occupyinglesion, the increased radial force may be advantageous. The disadvantageof a propensity for elongation is that great care must be taken whendelivering such a stent in a vessel or non-vascular tubular structure inorder to properly position it.

A further disadvantage of intravascular devices formed using a plainweave, is that they are often incapable of maintaining their shape whenbent. For example, when such a stent is being delivered through atortuous passageway with many turns, upon being bent, the weave of thestent tightens (e.g., the angle of the crossing wires approaches 180°).As a result of this tightening, the diameter of the stent increases andthe length of the stent decreases. Consequently, the diameter of thestent may exceed the diameter of the vessel or structure through whichit is traveling, impeding the delivery of the stent or causing the stentto lodge in the vessel. This problem may be due in part to the use ofweave materials such as stainless steel, which exhibit poor shapememory. This problem may also be due to the free, unclosed wires used toform the stent. The free sharp ends can create potential complicationsby penetrating, or perforating the wall of the tubular structure wheresuch a stent is placed. Further, steps that have been taken to eliminatethe free, sharp ends, such as connection with U-shaped members usingwelding, glue or the like (Wallsten, 1987) are time-consuming andexpensive. The delivery systems for such devices have also suffered fromproblems relating to the repositionability of the devices as they aredelivered into position in the living creature.

In stenting long arterial segments, the contiguously decreasing diameterof the arterial system from the center to the periphery may poseproblems. Woven stents with a uniform diameter will exert a substantialexpansile force to the vessel wall along the tapered portion.Additionally, the stent may remain more elongated in the taperedportion. In a study where WALLSTENTs with a uniform diameter were usedto bridge central venous obstruction in hemodialysis patients, it wasfound that the stents which were selected according to the size of thelarger diameter central vein exerted considerably higher force to thewall of the smaller caliber subclavian vein (Vesely, 1997).Simultaneously, the length of the stents in the smaller caliber vein waslonger than expected.

In the prior art, most of the filter designs except for the Bird's Nestfilter (Cook Inc., Bloomington, Ind.) have a conical shape and areanchored with multiple legs in the wall of the cava. The conical designis used because the main stream of the blood carries the thrombi fromthe lower part of the body through the center of the inferior vena cava.Therefore, all these devices are designed to have good filtrationcapacity at the center of the cava. The situation is quite differentafter some thrombi have been successfully captured. The center of thecava will no longer be patent and as a result, the blood will bediverted from the center to the periphery of the cava. Theaforementioned designs, however, are not capable of catching thrombieffectively at the periphery of the lumen so the patients willpractically be unprotected against subsequent peripheral embolization(Xian, 1995; Jaeger, 1998). Further, most of filters tend to be tiltedin the cava which can deter their thrombus-capturing efficacy.Additionally, except for the Simon nitinol filter (C. R. Bard, NewJersey, N.J.) the aforementioned designs require a fairly large invasivedelivery system of 10-F or larger.

The uniform caliber of cylindrical stents in the prior art used in theureter, as well as the peristalsis arrested at the proximal end of thestent, has resulted in severe hyperlasia of the urothelium andeventually occlusion of the ureter.

Turning to occluders, percutaneous occlusion techniques have becomeindispensable tools in minimally invasive management of a wide range ofpathological conditions. Use of permanent mechanical occlusion deviceshas been shown to be equivalent to that of surgical ligation. TheGianturco-Wallace stainless steel coil (Cook Inc., Bloomington, Ind.)has been the most widely used permanent, expandable intravascularocclusion device for transcatheter delivery (Gianturco et al., 1975).

Percutaneous coil embolization has been shown to be advantageous overtraditional surgical procedures in treatment of life threateninghemorrhage due to trauma or obstetric emergencies (Schwartz et al.,1993; Teitelbaum et al., 1993; Selby Jr., 1992; Levey et al., 1991;Ben-Menachem et al., 1991; Vedantham et al., 1997). Furthermore, coilshave been used alone or in combination with microvascular embolic agentsfor the treatment of vascular fistulas and malformations, tumors, andvarices (Wallace et al., 1979; Hendrickx et al., 1995; Furuse et al.,1997; White et al., 1996; Sagara et al., 1998; Punekar et al., 1996).During the last few years, the transcatheter closure of the patentductus arteriosus (PDA) with coils has become a frequently usedtechnique (Hijazi and Geggel, 1994; Hijazi and Geggl, 1997).

Although coil type occlusion devices have shown at least a degree ofutility, they have a number of drawbacks that could be significant insome applications. Intravascular stability of the coils has been shownto be highly dependent on proper matching of coil diameter with thediameter of the target vessel (Nancarrow et al., 1987), and with theexception of small vessels, a single coil rarely results in a stableocclusive thrombus (Hijazi and Geggel, 1994). Moreover, a long vascularsegment is often obliterated because of the frequent need for multiplecoils and the coils often remain elongated within the vessel becausetheir unconstrained diameter is larger than the vascular lumen.Furthermore, delayed recanalization rates of 37%-57% have been reportedin humans within 1-3 months after initially successful coil embolization(Sagara et al., 1998; 11 O'Halpin et al., 1984; Schild et al., 1994).

These and other drawbacks have inspired modifications in the design andtechnique of coil embolization. Recently, detachable microcoils andmacrocoils with controlled delivery have been designed to achieve a morecompact conglomerate of the coil and to prevent migration by allowingoptimal positioning of the coil before release (Zubillaga et al., 1994;Guglielmi et al., 1995; Marks et al., 1994; Reidy and Qureshi, 1996;Uzun et al., 1996; Tometzki et al., 1996; Dutton et al., 1995). However,since optimal arrangement of the coil alone may not prevent migration insome cases, such as high flow conditions or venous placement, a coilanchoring system has been devised (Knya et al., 1998). Although ananchoring system may stabilize a coil conglomerate within thevasculature, significantly reducing or eliminating the possibility ofcoil migration, such a system may render the coil non-repositionable.

Several different non-coil devices have been designed to achieve a morestable, limited size plug with higher hemostatic efficiency particularlyfor transcatheter closure of larger vessels (Schmitz-Rode et al., 1993;Kato et al., 1997; Knya et al., 1999) and PDAs (Pozza et al., 1995;Magal et al., 1989; Grifka et al., 1996). Recently, initial clinicalexperiences with a new self-expanding nitinol-mesh PDA occluder havebeen reported (Sharafuddin et al., 1996; Masura et al., 1998). A similarself-expanding, repositionable quadruple-disc device constructed of abraided nitinol mesh and polyester fibers has been reported to besuperior to standard Gianturco coils in experimental occlusion ofmid-size arteries (Sharaffuddin et al., 1996).

Although such non-coil devices may be repositionable, they too exhibitdrawbacks. For instance, the quadruple-disc device is severalcentimeters long in an elongated fashion, making difficult to keep thesuperselective position of the catheter tip during deployment. Themultiple rigid connections between the layers and the relative long andrigid connection between the occluder and the delivery cable furtherincrease this drawback. Although the nitinol mesh-PDA occluder hasdemonstrated utility, its proper placement requires a proper match bothin size and shape between the occluder and the lesion to be occluded.The type and quality of the connection between the occluder and thedelivery cable is the same as in the quadruple-disc design. A commondisadvantage of both designs is that they lack guidewire compatibility.As a result, a delivery catheter must often be navigated to the site ofocclusion first before an occluder may be loaded into the catheter anddelivered through it. Another relative disadvantage of both devices istheir cost of manufacturing.

Percutaneous catheter technique for permanent closure of isolatedpersistently patent ductus arteriosus (PDA) is now a treatment of choiceamong doctors, obviating open surgery. The configuration of the PDAvaries considerably. A majority of PDAs tend to have a funnel or conicalshape due to ductal smooth muscle constriction at the pulmonary arteryinsertion, although narrowings in the middle or aortic ends can beobserved (Krichenko, 1989). That is the reason why not only the size,but also the configuration, of the lesion plays a significant role inselecting an appropriate occluding device. Except from the small caliberlesions (with a maximum diameter of 2.5 mm or 3.3 mm, respectively),where some authors have achieved successful closure of the PDA withGianturco coils (Cambier, 1992; Lloyd, 1993; Sommer, 1994), Rashkind's“double umbrella” occluder is the most often used device for thispurpose (Rashkind, 1987; Hosking, 1991; Latson, 1991; Wessel, 1988;Report of the European Registry, 1992). It is available in two sizes(with a diameter of 12 mm and 17 mm) which require a 8-F and 11-Fdelivery system, respectively.

In the majority of cases, the deployment of the traditional PDA deviceis performed from a femoral vein access (Report of the EuropeanRegistry, 1992). Because of the size of the delivery sheath, such adevice is not suitable for the treatment of patients with a body weightof less than 8 kg. Using even a larger umbrella, this procedure is notrecommended for the treatment of the lesions with a diameter of 8 mm orabove (Latson, 1991). About 80% of unselected patients with isolated PDAare candidates for the Rashkind device using the aforementioned criteria(Latson, 1991). With the Rashkind device, the proportion of patientswith residual flow through the lesion fell from 76% immediately afterimplantation to 47% by the day after implantation and to 17% by a yearafter implantation (Report of the European Registry, 1992). According tosome authors the residual flow carries a potential risk of infectiveendocarditis and should be avoided if possible. Its abolishment can beachieved by implantation of another device or surgery.

One of the main drawbacks of the Rashkind umbrella is that it is notsuitable for occlusion of all types of PDA. Preferably, it is used toocclude short PDAs with relatively wide end-openings. Its two discscover both the pulmonary and the aortic opening of the PDA. Longer PDAmay hinder the discs to be positioned in the proper way, that is,parallel to each other, thereby deteriorating its self-anchoring.Another disadvantage of the umbrella is that the occluding capacity ofthe design depends exclusively on the thrombogenicity of the porousDacron material, frequently resulting in partial and lengthy occlusion.

For the majority of patients with urinary leakage and/or fistulas(mainly due to tumor propagation to their ureters), the diversion ofurine is currently performed by a percutaneous transrenal approachtogether with ureteral occlusion. Formerly, detachable and nondetachable balloons were used for this purpose, but they did not causesatisfactory ureteral occlusion. Migration as well as deflation of theballoons occurred relatively frequently (Gunter, 1984; Papanicolau,1985) leading to recurrence of the urine leakage. A silicone ureteraloccluder was developed and used with only limited success because ofdevice migration (Sanchez, 1988). This resulted in repositioning andconsequent incomplete ureteral occlusion. It appears that the bestresults have been accomplished with Gianturco coils and Gelfoamembolization (Gaylord, 1989; Bing, 1992 a; Farrel, 1996). Even withmultiple coil placements, together with Gelfoam plugs, the ureteralocclusion may sometimes be achieved for only weeks or months, and wasattributed mostly to the induced urothelial hyperplasia (Bing, 1992 b).Coil migration was frequently encountered in these studies. The lack ofappropriate self-anchoring results in coil migration which eventuallydeteriorates the occlusive effect.

Problems pointed out in the foregoing are not intended to be exhaustivebut rather are among many that tend to impair the effectiveness ofpreviously known stents, occluders and filters. Other noteworthyproblems may also exist; however, those presented above should besufficient to demonstrate that previous techniques appearing in the arthave not been altogether satisfactory, particularly in providingflexible, self-expanding, repositionable stents, occluders and filters.

SUMMARY OF THE INVENTION

The present invention overcomes the problems inherent in the prior artby providing a self-expandable, repositionable device for use as astent, an occluder, or a filter which may be formed using a plain weave,and may have closed structures at both its ends.

In one respect, the invention is a device that includes, but is notlimited to, a plurality of shape memory wires woven together to form abody suitable for implantation into an anatomical structure. The bodyhas first and second ends. The shape memory wires cross each other toform a plurality of angles, at least one of the angles being obtuse.Both ends of at least one shape memory wire are located proximate oneend of the body. The value of the obtuse angle is increased when thebody is axially compressed.

The shape memory wires may be made of nitinol. The shape memory wiresmay be made of FePt, FePd or FeNiCoTi. The shape memory wires may bemade of FeNiC, FeMnSi or FeMnSiCrNi. The shape memory wires may eachhave a diameter ranging in size from about 0.006 inches to about 0.012inches. The plurality of shape memory wires may include at least 6 shapememory wires. The body may have a tubular shape with a substantiallyuniform diameter. The body may have a tapered shape with a diameter thatdecreases from one end of the body to the other end of the body. Thebody may have a generally hourglass shape. As used herein, “a generallyhourglass” shape is a shape that resembles a body having two ends thatare larger in terms of cross-sectional area than a mid-portion locatedtherebetween. Such shapes include those resembling traditionalhourglasses or dumbbells, for example. The body may be woven by hand.The body may be woven by a machine, such as a braiding machine.

The device may also include, but is not limited to, a graft materialattached to the body. The graft material may be made from wovenpolyester. The graft material may be made from Dacron. The graftmaterial may be made from polyurethane. The graft material may be madefrom PTFE. The graft material may partially cover the body. As usedherein, a graft material that “partially covers” a body is attached tothe body such that a portion of the wire or wires forming the body areleft bare or exposed. As a result of only partially covering a body,blood or other bodily fluids may flow through the bare portion of thebody relatively unimpeded by the graft material.

The device may also include, but is not limited to, a first tube that isconfigured to accept a guide wire and a second tube that is configuredto fit over the first tube. Prior to delivering the body into ananatomical structure, the second tube is placed over the first tube, oneend of the body is secured to the first tube and the other end of thebody is secured to the second tube.

In another respect, the invention is a device that includes, but is notlimited to, a body suitable for implantation into an anatomicalstructure. The body has a first end, a second end and is defined by atleast n shape memory wires, wherein n is greater than one. The n shapememory wires are arranged such that the body includes a first portion.The first portion includes a first woven portion and at least one strut.The shape memory wires of the first woven portion cross each other toform a plurality of angles, at least one of the angles being obtuse.Both ends of at least one shape memory wire are located proximate oneend of the body. The value of the obtuse angle is increased when thebody is axially compressed.

The shape memory wires may be made from nitinol. The shape memory wiresmay be made from FePt, FePd or FeNiCoTi. The shape memory wires may bemade of FeNiC, FeMnSi or FeMnSiCrNi. The first portion may include afirst woven portion separated from a second woven portion by multiplefirst struts.

The body may also include, but is not limited to, a second portionlocated adjacent to the first portion. The second portion includes asecond woven portion. The second portion has n+x shape memory wires, andx is at least one. The first portion may have a generally domed shape.The first woven portion may have a generally domed shape and themultiple first struts may be bent slightly so as to increase theself-anchoring capability of the body in an anatomical structure. Thefirst portion may also include a third woven portion separated from thesecond woven portion by multiple second struts. The first and thirdwoven portions may have generally domed shapes.

The device may also include, but is not limited to, a graft materialattached to the body. The graft material comprises may be made fromwoven polyester. The graft material may be made from Dacron. The graftmaterial may be made from polyurethane. The graft material may be madefrom PTFE. The graft material may partially cover the body.

The device may also include, but is not limited to, a first tube that isconfigured to accept a guide wire and a second tube that is configuredto fit over the first tube. Prior to delivering the body into ananatomical structure, the second tube is placed over the first tube, oneend of the body is secured to the first tube and the other end of thebody is secured to the second tube.

In another respect, the invention is a device that includes, but is notlimited to, a plurality of biodegradable filaments woven together toform a self-expanding body suitable for implantation into an anatomicalstructure. The self-expanding body has a first end and a second end. Thebiodegradable filaments cross each other to form a plurality of angles,at least one which is obtuse. The value of the obtuse angle is increasedwhen the body is axially compressed.

The biodegradable filaments may be made from polyglycolic acid. Thebiodegradable filaments may be made from poly-L-lactic acid. Thebiodegradable filaments may be made from a polyorthoester. Thebiodegradable filaments may be made from a polyanhydride. Thebiodegradable filaments may be made from a polyiminocarbonate. Thebiodegradable filaments may be made from an inorganic calcium phosphate.The biodegradable filaments may include about 0.05 to 0.25 percent byweight of calcium oxide, calcium hydroxide, calcium carbonate, calciumphosphate, magnesium oxide, magnesium hydroxide, magnesium carbonate,magnesium phosphate, sodium phosphate or potassium sulfate. Thebiodegradable filaments may be made from a polymer having about 15 toabout 30 mole percent glycolide. At least one of the biodegradablefilaments may be made from paclitaxel, docetaxel or heparin. Both endsof at least one biodegradable filament may be located proximate thefirst end of the self-expanding body. Each end of the self-expandingbody may include at least one closed structure.

The device may also include, but is not limited to, at least one shapememory wire secured to the self-expanding body. Both ends of the oneshape memory wire may be located proximate one end of the self-expandingbody.

In another respect, the invention is a method of creating a bodysuitable for implantation into an anatomical structure. The body has twoend ends. The method includes, but is not limited to, bending the shapememory wires in a plurality of shape memory wires to create bentportions in the shape memory wires. The bent portions are arranged todefine one end of the body. Each shape memory wire has two ends. Themethod also includes, but is not limited to, weaving the ends of theshape memory wires to create the body such that the shape memory wirescross each other to form a plurality of angles, at least one of theangles being obtuse. The value of the obtuse angle is increased when thebody is axially compressed.

The bent portions may be bends or loops. The shape memory wires may bemade from nitinol. The shape memory wires may be made of FePt, FePd orFeNiCoTi. The shape memory wires may be made of FeNiC, FeMnSi orFeMnSiCrNi. The shape memory wires may each have a diameter ranging insize from about 0.006 inches to about 0.012 inches. The plurality ofshape memory wires may include at least 6 shape memory wires. The bodymay have a tubular shape with a substantially uniform diameter. The bodymay have a tapered shape with a diameter that decreases from one end ofthe body to the other end of the body. The body may have a generallyhourglass shape. The body may be woven by hand. The body may be woven bya machine, such as a braiding machine.

In another respect, the invention is a method of creating a bodysuitable for implantation into an anatomical structure. The body has twoends. The method includes, but is not limited to, providing a weavingsystem that includes a template having first template projections. Themethod also includes, but is not limited to, bending shape memory wiresaround the first template projections to create bent portions in theshape memory wires. The bent portions are arranged to define one end ofthe body. Each shape memory wire has two ends. The method also includes,but is not limited to, weaving the ends of the shape memory wires aroundthe template to create the body such that the shape memory wires crosseach other to form a plurality of angles, at least one of the anglesbeing obtuse. The value of the obtuse angle is increased when the bodyis axially compressed.

The first template projections may be tabs. The first templateprojections may be pins. The pins may be attached to a ring engaged withthe template. The weaving system may also include, but is not limitedto, a first weaving plate configured to rotate in a first directionduring the weaving. The weaving system may also include, but is notlimited to, first bobbins arranged on the first weaving plate, and oneend of each shape memory wire is attached to each first bobbin prior tothe weaving. The weaving system may also include, but is not limited to,a second weaving plate configured to rotate in a second direction duringthe weaving, and the second weaving plate is spaced apart from the firstweaving plate. The weaving system may also include, but is not limitedto, second bobbins arranged on the second weaving plate, and one end ofeach shape memory wire is attached to each second bobbin prior to theweaving. The method may also include, but is not limited to, securingthe shape memory wires to the template. The method may also include, butis not limited to, forming closed structures with the ends of the shapememory wires. The closed structures may be arranged to define the otherend of the body. The method may also include, but is not limited to,heating the body and the template.

In another respect, the invention is a device for delivering an axiallyand radially expandable woven body having two ends into an anatomicalstructure. The device includes, but is not limited to, a first tubeconfigured to accept a guide wire, and a second tube configured to fitover the first tube. When the tubes are used for delivering the axiallyand radially expandable woven body, one end of the axially and radiallyexpandable woven body is secured to the outside of the first tube andthe other end of the axially and radially expandable woven body issecured to the outside of the second tube.

In another respect, the invention is a device for delivering an axiallyand radially expandable woven body having two ends into an anatomicalstructure. The device includes, but is not limited to, a first tubeconfigured to accept a guide wire. The first tube has at least one pairof first tube holes that are positioned proximate one end of the firsttube. The device also includes, but is not limited to, a second tubeconfigured to fit over the first tube. The second tube has at least onepair of second tube holes that are positioned proximate one end of thesecond tube. The device also includes, but is not limited to, a firstsecuring wire configured to be threaded through the pair of first tubeholes. The device also includes, but is not limited to, a secondsecuring wire configured to be threaded through the pair of second tubeholes. When the tubes are used for delivering the axially and radiallyexpandable woven body, one end of the axially and radially expandablewoven body is secured to the outside of the first tube with the firstsecuring wire and the other end of the axially and radially expandablewoven body is secured to the outside of the second tube with the secondsecuring wire.

In another respect, the invention is an occluding system that includes,but is not limited to, a plurality of shape memory wires woven togetherto form a body useful for occluding an anatomical structure. The bodyhas first and second ends. Both ends of at least one shape memory wireare located proximate one end of the body. The shape memory wires crosseach other to form a plurality of angles, at least one of the anglesbeing obtuse. The value of the obtuse angle is increased when the bodyis axially compressed.

The shape memory wires may be made from nitinol. The occluding systemmay also include, but is not limited to, an occluding agent enclosedwithin the body. The occluding agent may include one or more threads ofpolyester. The occluding agent may also include, but is not limited to,one or more threads of DACRON. The occluding system may also include ajacket coupled to the body. The jacket may be made from silicone. Thejacket may be made from polyurethane. The occluding system may alsoinclude, but is not limited to, a first tube configured to accept aguide wire, and a second tube configured to fit over the first tube.Prior to delivering the body into an anatomical structure, one end ofthe body is secured to the outside of the first tube and the other endof the body is secured to the outside of the second tube.

In another respect, the invention is a device that includes, but is notlimited to, a body suitable for implantation into an anatomicalstructure. The body has an axis, a first end and a second end. The bodyis made from a shape memory wire that has a first segment and a secondsegment. The segments are separated by a bend in the shape memory wirethat is located proximate one end of the body. The first segment extendshelically in a first direction around the axis toward the other end ofthe body. The second segment extends helically in a second directionaround the axis toward the other end of the body. The first and secondsegments cross each other in a plurality of locations.

The first segment may be positioned farther from the axis than thesecond segment at least one location. The first segment may bepositioned farther from the axis than the second segment at eachlocation. The shape memory wire may be made from nitinol. The device mayalso include a first tube configured to accept a guide wire, and asecond tube configured to fit over the first tube. Prior to deliveringthe body into an anatomical structure, one end of the body is secured tothe outside of the first tube and the other end of the body is securedto the outside of the second tube.

In another respect, the invention is a device that includes, but is notlimited to, a body suitable for implantation into an anatomicalstructure. The body has a first end and a second end. The body is formedfrom a shape memory wire that has a first segment and a second segment.The segments are separated by a bend in the wire that is locatedproximate one end of the body. The first segment and second segments arearranged to form loops and twisted segments such that at least twocontiguous loops are separated from another loop by a twisted segment.The definition of “contiguous” is set forth below with reference to thefigures herein for the sake of clarity.

At least three contiguous loops may be separated from another loop by atwisted segment. At least four contiguous loops may be separated fromanother loop by a twisted segment. At least two contiguous loops may beseparated from two other contiguous loops by a twisted segment. Theshape memory wire may be made from nitinol. The device may also include,but is not limited to, a first tube configured to accept a guide wire,and a second tube configured to fit over the first tube. Prior todelivering the body into an anatomical structure, one end of the body issecured to the outside of the first tube and the other end of the bodyis secured to the outside of the second tube.

In another respect, the invention is a device that includes a bodysuitable for implantation into an anatomical structure. The body has,but is not limited to, two ends and is formed from a shape memory wirethat has a first segment and a second segment. The segments areseparated by a bend in the wire that is located proximate one end of thebody. The segments are positioned adjacent to each other inloop-defining locations. The segments also extend between theloop-defining locations in spaced relation to each other so as form atleast two loops. At least one of the at least two loops has a compressedshape. The definition of a “compressed” shape is set forth below withreference to the figures herein for the sake of clarity.

The shape memory wire may be made from nitinol. The segments may besecured together using welds at the loop-defining locations. Thesegments may be secured together with collars at the loop-defininglocations. The body may also include, but is not limited to, at leastone coil placed over at least a portion of one of the segments, and, asa result, the body may be used as an occluder. The body may also includeat least one fiber attached to the coil. The device may also include,but is not limited to, a first tube configured to accept a guide wire,and a second tube configured to fit over the first tube. Prior todelivering the body into an anatomical structure, one end of the body issecured to the outside of the first tube and the other end of the bodyis secured to the outside of the second tube.

The present invention also provides a delivery system that may secureboth the proximal and distal ends of the stent, occluder or filter.Advantageously, this delivery system allows the stent, occluder orfilter to be easily repositioned as it is being delivered into place. Asa result, the stent, occluder or filter may be more precisely positionedwithin the living creature.

One advantage of the present invention is the unique fixation method ofthe tapered stent. The tapered shape of the stent allows the stent to befixed in a tapered vessel or tubular structure with less radial orexpansile force than a straight stent might exhibit, thus potentiallyresulting in a less hyperplastic intimal reaction.

The straight stent of the present invention exhibits a high expansileforce and thus a large capability of withstanding outer compression.This may be especially advantageous in tumorous stenoses, or fibrousstrictures (including radiation-induced stenoses) where stents withinadequate expansile forces can be easily compressed and/or areincapable of assuming their nominal shape and diameter. In some cases,even the stenoses of arteriosclerotic origin can be so calcified (e.g.,iliac or renal artery stenoses) that extra radial force is required fromthe stent to hold the patency of the vessel. Furthermore, the wovenintravascular devices of the present invention are also able to returnto their original, unconstrained shape after being bent, even maximally.

Advantageously, the stents, occluders and filters of the presentinvention do not possess free, sharp wire ends. Thus, many potentialcomplications are eliminated (Prahlow, 1997). Additionally, the tightmesh of the stents of the present invention coupled with the use ofnitinol wires, for example, makes them easy to monitor underfluoroscopy.

The present invention also includes a group of self-expanding,self-centering cava filters woven from materials as described above suchthat a coherent element is formed that without the use of a joint orattachment between the portions of the filters. The cava filters of thepresent invention provide increased filtrating efficiency not only atthe center but also at the periphery of the cava. Additionally, thehourglass filter of the present invention utilizes multiple filtrationlevels. The cava filters of the present invention are able toself-center due to the symmetrical nature of their design and theirpotentially flared base.

The cava filters of the present invention may utilize a relativelysmall, 7 French delivery catheter or sheath. Additionally, the superbflexibility of the cava filters makes it possible to deliver them viaany of the possible access sites of the human body (femoral, jugular,antecubital veins).

The cava filters of the present invention may utilize a relativelysmall, 7 French delivery catheter or sheath. Additionally, the superbflexibility of the cava filters makes it possible to deliver them viaany of the possible access sites of the human body (femoral, jugular,antecubital veins).

The present invention also includes a bi-iliac filter (“BI filter”) thatis a low-profile, self-expanding, flexible, temporary filter which maybe woven from a number of superelastic or shape memory alloys. The BIfilter is a type of temporary filter that can be deployed from eitherfemoral vein, and it can filtrate the blood at the iliac veins/inferiorcava junction. The BI filter of the present invention typically works ata low level of venous circulation. Advantageously, the BI filtersimultaneously filters all the blood coming from both iliac veins,achieving almost 100% filtration. Further, the use of the BI filter isparticularly beneficial in perioperative and posttraumatic cases.

The inverse U-shape of the BI filter together with the expansile forceof the tubular weave ensures firm position along the iliac/cavajunction. A further advantage of the present invention is that the BIfilter may utilize a relatively small, 7 French delivery catheter orsheath. Further, due to the flexibility of the mesh of the BI filter,the delivery system thereof may be advanced from ipsi- to contralateraliliac vein. As with the cava filters, the BI filter may possess anon-ferromagnetic character making it MRI compatible.

The BI filter is suitable for temporary filtration. The BI filter allowsfor removal of the entrapped thrombi safely and successfully beforeremoval of the filter. Using an adequately sized sheath, the smallthrombus fragments entrapped within the mesh could also be removedtogether with the filter.

The stents of the present invention can be advantageously covered withmaterials such as silicone, polyurethane, and/or an anticancer coatingagent that allow the stents to reduce the possibility of restenosisafter delivery, and which also allow the stents to be used in stentingmalignant stenoses, for example. The filters of the present inventionmay also be covered with anticoagulant coating agents.

Ureter strictures/compression/occlusion may be stented with theseuncovered and/or covered stents; in particular, the use of a longtapered stent may advantageously match the special conditions posed bythe different caliber and distensibility of the different segments ofthe ureter as well as the constant peristalsis.

The stents of the present invention can also be used in somenon-vascular applications including biliary tree and tracheo-bronchialsystem if the lesion does not require a bifurcated stent.

The stents, occluders and filters of the present invention may be usedin many different applications. They provide the advantages of superbflexibility, repositionability/removability, and precisepositionability.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings form part of the present specification and areincluded to further demonstrate certain aspects of the presentinvention. The invention may be better understood by reference to one ormore of these drawings in combination with the description ofillustrative embodiments presented herein.

FIG. 1A is a perspective view of a stent according to one embodiment ofthe present invention.

FIG. 1B is a front view of a stent end defined by bends according to oneembodiment of the present invention.

FIG. 1C is a perspective view of one wire of a stent according to oneembodiment of the present invention.

FIG. 2 is a side view of the arrangement of wires in a plain weaveaccording to one embodiment of the present invention.

FIG. 3 is a perspective view of a delivery system according to oneembodiment of the present invention.

FIG. 4 is a side view of a delivery system according to one embodimentof the present invention.

FIGS. 5A-E sequentially illustrative steps in a delivery methodaccording to one embodiment of the present invention.

FIG. 6 is a front view of a conical filter having bends or loops in theproximal (rear) end thereof according to one embodiment of the presentinvention.

FIG. 7 is a front view of a conical filter having bends or loops in thedistal (front) end thereof according to one embodiment of the presentinvention.

FIG. 8 is a front view of a dome filter having bends or loops in thedistal end thereof according to one embodiment of the present invention.

FIG. 9 is a front view of an hourglass filter according to oneembodiment of the present invention.

FIG. 10 is a front view of an hourglass filter according to oneembodiment of the present invention placed in the Inferior Vena Cava.

FIG. 11 is a front view of a bi-iliac filter according to one embodimentof the present invention placed in the iliac veins.

FIG. 12 is a front view of a bi-iliac filter having a retrieval loopaccording to one embodiment of the present invention placed in the iliacveins.

FIG. 13 is a front view of a bi-iliac filter having a retrieval loop anda stabilizing wire according to one embodiment of the present inventionplaced in the iliac veins.

FIG. 14 is a is a perspective view of a tapered stent according to oneembodiment of the present invention.

FIG. 15 is a perspective view of a single wire embodiment filteraccording to one embodiment of the present invention.

FIGS. 16-24 show stages in a hand weaving method according to oneembodiment of the present invention.

FIG. 25 is a front view of the proximal portion of a delivery systemaccording to one embodiment of the present invention.

FIG. 26 is a front view of a delivery system for a temporary filteraccording to one embodiment of the present invention.

FIGS. 27A and B illustrate stages in the removal of a filter from avessel according to one embodiment of the present invention.

FIG. 28 is a front view of a conical filter in a fully stretchedposition according to one embodiment of the present invention.

FIG. 29 is a projected cross section of an hourglass filters takenacross the middle portion of the filter according to one embodiment ofthe present invention.

FIG. 30A is a front view of two wires coupled together for use in a handweaving method according to one embodiment of the present invention.

FIG. 30B is a perspective view of the placement of two wires eachcoupled to a pin for use in a hand weaving method according to oneembodiment of the present invention.

FIG. 31 is a perspective view of a biodegradable stent with areinforcing wire according to one embodiment of the present invention.

FIG. 32 is a perspective view of a biodegradable stent with areinforcing wire according to a second embodiment of the presentinvention.

FIGS. 33A-G are front views of various configurations of an occluderaccording to the present invention.

FIG. 34 is a front view of an occluder having a jacket according to oneembodiment of the present invention.

FIG. 35 is a front view of an occluder having clips according to oneembodiment of the present invention.

FIG. 36 is a front view of an aneurysm being treated by transcatheterembolization according to one embodiment of the present invention.

FIG. 37 is perspective view of a template with longitudinal tabs aroundwhich wires are bent according to one embodiment of the presentinvention.

FIG. 38A is an enlarged perspective view of the longitudinal tab andbent wire depicted in FIG. 37 according to one embodiment of the presentinvention.

FIG. 38B is an enlarged perspective view of a longitudinal tab depictedin FIG. 37 around which a wire is bent to form a loop according to oneembodiment of the present invention.

FIG. 39 is a perspective view of a wire bent around a longitudinal taband wrapped around a pair of bobbins according to one embodiment of thepresent invention.

FIG. 40 is a top view of inner and outer weaving plates provided withbobbins according to one embodiment of the present invention.

FIG. 41 is a perspective view depicting an upper weaving plate providedwith bobbins and wires, a partial cross-sectional view of a lowerweaving plate provided with bobbins and wires, and a partialcross-sectional view of a template around which both plates are arrangedaccording to one embodiment of the present invention.

FIG. 42A is a top view of upper and lower weaving plates provided withbobbins and wires and arranged around a template, and illustrates thefirst crossing of the wires according to one embodiment of the presentinvention.

FIG. 42B is a front view of a small caliber loop formed by bending awire according to one embodiment of the present invention.

FIG. 43A is a top view of upper and lower weaving plates provided withbobbins and wires and arranged around a template, and illustrates thefirst crossing of the wires according to another embodiment of thepresent invention.

FIG. 43B is a front view of a bend formed by bending a wire according toone embodiment of the present invention.

FIG. 44 is a perspective view of upper and lower weaving plates providedwith bobbins and arranged around a template such that the surfaces ofthe weaving plates from which the bobbin rods extend face each otheraccording to one embodiment of the present invention.

FIG. 45 is a perspective view of upper and lower weaving plates providedwith bobbins and wires and arranged around a template such that thesurfaces of the weaving plates from which the bobbin rods extend faceeach other according to one embodiment of the present invention.

FIG. 46A is a perspective, partial cross-sectional view of a tool fortwisting the wire ends of a woven body according to one embodiment ofthe present invention.

FIG. 46B is a cross-sectional view of the jaws and outer housing of thetool illustrated in FIG. 46A.

FIG. 47A is a perspective view of a body woven around a template havinglongitudinal and transverse tabs according to one embodiment of thepresent invention.

FIG. 47B is an enlarged perspective view of one of the transverse tabsand twisted wire ends depicted in FIG. 47A according to one embodimentof the present invention.

FIG. 48 is a perspective view of a template around which a ring havingfinish pins has been threadably engaged according to one embodiment ofthe present invention.

FIG. 49 is a perspective view of a template having finish holes throughwhich finish pins may be placed according to one embodiment of thepresent invention.

FIG. 50A is a front view of a stent formed from a single wire accordingto one embodiment of the present invention.

FIG. 50B is a front view of a stent formed from a single wire accordingto a second embodiment of the present invention.

FIG. 50C is a front view of a stent formed from a single wire accordingto a third embodiment of the present invention.

FIG. 50D is a perspective view of the stent depicted in FIG. 50Bpositioned on a template according to one embodiment of the presentinvention.

FIG. 51 is a perspective view of a barbless stent filter according toone embodiment of the present invention.

FIG. 52 is a perspective view of a barbless stent filter having bentlongitudinal segments according to one embodiment of the presentinvention.

FIG. 53 is a perspective view of a barbless stent filter having twofiltrating levels according to one embodiment of the present invention.

FIG. 54 is a front view of two stents placed in side-by-siderelationship with each other in the aorta according to one embodiment ofthe present invention.

FIG. 55 is a perspective view of two partially-covered stents placed inside-by-side relationship with each other in the aorta according to oneembodiment of the present invention.

FIG. 56 is a perspective view of a stent having struts placed inside-by-side relationship with another stent in the aorta according toone embodiment of the present invention.

FIG. 57A is a front view of an occluder formed from a single wire arounda template according to one embodiment of the present invention.

FIG. 57B is a perspective view of an occluder formed from a single wirethat includes collars placed around the wire segments at loop-defininglocations according to one embodiment of the present invention.

FIG. 57C is a top view of an occluder formed from a single wire that hascoil pieces placed over portions of the wire segments located betweencollars according to one embodiment of the present invention.

FIG. 57D is a top view of an occluder formed from a single wire that hascoil pieces placed over portions of the wire segments located betweencollars and also has thrombogenic filaments attached to the coil piecesaccording to one embodiment of the present invention.

FIGS. 58A-D show stages in the delivery of one stent of a pair of stentsin the aorto-renal junction according to one embodiment of the presentinvention.

FIG. 59 is a front view of a barb (of a filter) that is penetrating avessel wall according to one embodiment of the present invention.

FIG. 60 is a perspective view of a single wire embodiment filteraccording to another embodiment of the present invention.

FIG. 61 is a front view of upper and lower weaving plates supported by aweaving plate supporter according to one embodiment of the presentinvention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 1. Stents Straight Stents

With reference to the illustrative embodiment shown in FIG. 1A, there isshown a stent for insertion and delivery into an anatomical structure.The stent includes a plurality of wires 5 which may be arranged in aplain weave so as to define an elastically deformable body 10. As usedherein, “elastically deformable” means that the deformation of such abody is non-permanent and an original or initial shape may besubstantially recovered, or regained, upon the release of a force (whichmay be mechanical, electromagnetic, or any other type of force). As usedherein, “substantially recovered” means that recovery need not be suchthat the exact, original shape be regained. Rather, it means that somedegree of plastic deformation may occur. In other words, recovery neednot be total. Such elastic deformability may be achieved by utilizingthe superelastic properties of suitable shape memory wires, which arediscussed below.

U.S. Pat. No. 4,655,771 to Wallsten (1987), which is hereby expresslyincorporated by reference, displays the manner in which wires cross eachother using plain weave as shown in FIG. 1 a therein. FIG. 2 alsoillustrates the manner in which the wires 5 of the present intravasculardevices may be arranged utilizing a plain weave.

Body 10 is both radially and axially expandable. Body 10 includes frontor distal end 12 and rear or proximal end 2. As shown in FIG. 1A, end 12has a plurality of closed structures. These closed structures may besmall closed loops 6 or bends 8 (FIG. 1B). Both bends 8 and small closedloops 6 may be formed by bending a wire 5 at a selected point locatedbetween the ends 7 of wire 5 (FIG. 1C shows small closed loops 6). Formost applications, the selected point of the bend or small closed loopmay be close to the midpoint of wire 5, as shown in FIG. 1C with respectto small closed loop 6. FIG. 1C also shows both ends of wire 5 beinglocated proximate end 2 of body 10 (although the remainder of body 10 isnot shown). Body 10 is formed by plain weaving wires 5, as will bediscussed below in greater detail.

Loops 6 and bends 8 provide significant advantages, some of which areunexpected, over woven devices such as the WALLSTENT that have free wireends. For instance, the Wallsten patent recognizes that the free wireends of the WALLSTENT should be protected, implicitly acknowledging thepotential tissue-damaging dangers such free, sharp wire ends pose. TheWallsten patent suggests methods by which one can attempt to lessenthese dangers, such as connecting the free wire ends to each other byattaching U-shaped members to them through heat welding, gluing or thelike. These suggested methods can be time-consuming and, as a result,expensive. No such steps need to be taken in creating either loops 6 orbends 8 of the present woven devices as will be discussed below ingreater detail.

Further, the connections resulting from the methods disclosed in theWallsten patent are likely more prone to mechanical failure than areloops 6 or bends 8 of the present woven devices. For example, weldingcan introduce anomalies such as cracks (which may result from thenon-uniform solidification, uneven boundaries, etc.); voids or otherirregularities resulting from porosity; inclusions (which include slag,oxides, etc.); etc., into the welded metal that create stressconcentrations and dramatically increases the propensity for the weldedconnection to fail at those locations. In contrast, the gentle curvesand bends resulting in loops 6 and bends 8 are virtually free of anysuch induced stresses and, as a result, are much less likely to fail.

The Wallsten patent also suggests gluing the free wire ends, a methodthat provides even less structural integrity than can welding, becausethe resulting bond between the joined wire ends is only as strong as thesurface tension between the glue and the metal used. Consequently, thejoint created is more prone to failure than a welded joint sufferingfrom the anomalies just discussed.

Similarly, the Wallsten patent discloses first utilizing electricresistance heating to weld together the points of crossing of the freewire ends in a ring around the stent and then folding the free wire endsextending beyond the welded ring inwardly with light plastic deformationthrough controlled heating. This method involves not only the likelyintroduction of the anomalies discussed above that can result fromwelding, it also involves an additional stress on the joints created asthe free wire ends are folded inwardly while being heated. Thus, thispreferred joint is similar to the glued joint in that it is likely evenmore prone to failure than one involving only welding.

In sum, the gentle curves and bends that may be used to create loops 6and bends 8 of the present woven devices provide devices with saferends: no free wire ends exist that may unintentionally penetrate anddamage the wall of the structure into which they are delivered; thebends 8 or loops 6 are much less likely to mechanically fail than arethe free wire ends that are connected together using welding or glue;and the likely time-consuming task of creating multiple welded or gluedjoints does not exist. Further, while the closed structures 4 (discussedbelow in greater detail) may be reinforced using methods similar tothose suggested by the Wallsten patent (i.e., such as by welding), thepresent woven devices have, at most, only half as many potentiallocations for using such methods (and most likely less than halfconsidering fewer wires are generally needed for making the presentstents than are needed for making comparably-sized WALLSTENTS, evenequating one of the present wires to two wires as those are used in theWALLSTENT). As a result, the potential for mechanical failure of thepresent woven devices is reduced accordingly.

In addition to the foregoing benefits, loops 6 and bends 8 also provideadvantages over the modified free wire ends disclosed in the Wallstenpatent discussed above that are unexpected. For example, the inventorshave found that the mesh of one of the present woven stents may beformed from fewer wires than can the mesh of a comparably-sizedWALLSTENT (even equating one of the present wires to two wires as thoseare used in the WALLSTENT). Accordingly, the expansile force of one ofthe present woven stents of a given size may be maintained with fewerwires than would be needed to maintain the same expansile force of aWALLSTENT of the same size by simply increasing the mesh tightness(i.e., by increasing angle a—FIG. 1A—discussed below in greater detail).Similarly, the inventors have found that the same result may be achievedby increasing the diameter of the present wires with or withoutadjusting the mesh tightness. As a result, the amount of metal neededfor the present woven stents may be less than what is needed in anothercomparably-sized woven stent, such as the WALLSTENT. This reduction innecessary metal translates to a cost savings, and, as described above,also means that patients are less likely to experience thrombosis and/orrestenosis. As a further result, the variety of sizes that may becreated for the present stents and the variety in the tightness of theweave of each is virtually unlimited, thereby facilitating virtually allpotential applications.

Further, the inventors also discovered that virtually no shorteningoccurs while bending the present woven stents, nor do the diameters ofthe present woven stents increase during bending. Thus, it is easier toaccurately and predictably position the present stents in a tortuousanatomy than it is to position other woven stents that shorten more orsuffer larger increases in diameter when bent, such as the WALLSTENT.For example, a tightly-woven present stent, 2.5 cm long, 10 mm indiameter, formed from 10 0.006-inch wires may be maximally bent bysimply holding the two ends thereof between two fingers and bringingthose ends together, and no shortening or diameter increase occursduring maximal bending. In contrast, for a WALLSTENT formed from 240.005-inch wires to behave similarly, the inventors found that it shouldbe 6 cm long and 9 mm in diameter; although, when manipulated in asimilar manner, the WALLSTENT experienced a 10% increase in diameter andsome shortening. Thus, the length-to-diameter ratios of the foregoingstents were 2.5 and 6.6, respectively.

As few as five wires, and an unlimited maximum number of wires may beused to form body 10 for any given application. As used herein, “wires”will mean a strand formed of any material, such as metal, plastic,fiber, etc. In an exemplary embodiment of the present invention, 6 to 12wires are typically used to form body 10 in most applications.

The number of wires that may be used depends on the application, andspecifically on the desired expansile force of the stent. The expansileforce of the stent is the radial force necessary to reduce the diameterof the stent. Factors affecting the expansile force of the stentinclude: the tightness of the weave (which is determined by the numberof wires used and the angle formed by the crossed wires—the more wiresor the closer the angle is to 180°, the tighter the weave), the numberof wires used to form the woven stent, and the diameter of the wiresused. When body 10 is used in the coronary artery, for example, it maybe desirable to use the smallest possible amount of wire material toprevent thrombosis and reduce the possibility of restenosis in thevessel with a relatively slow circulation.

In FIG. 1A, when body 10 is in its initial, unconstrained shape, angle amay range from about 90° up to, but not including, 180°. The expansileforce of body 10 increases as angle a approaches 180°. It is to beunderstood that angles less than 90° may be utilized for angle a. In anexemplary embodiment, angle a is preferably obtuse, i.e., more than 90°,and most preferably about 150°. In certain applications, however, alarger expansile force may be desirable, and, thus, angle a may becloser to 180°, such as in the case of a tumorous stricture or the like.In this regard, in an in vitro comparative study, a stent according tothe present invention exhibited a higher expansile force and thus alarger capability of withstanding outer compression than both a Z-stentand a WALLSTENT of the same diameter, as revealed in Table 1, below. InTable 1, the designation Δ in the leftmost column represents thecircumferential displacement (in mm) of the stent in question. Forexample, a Δ of 2 mm indicates that the circumference of the stent inquestion was reduced by 2 mm, and the force necessary to effect thatdisplacement was then recorded. The designation “W” refers to theWALLSTENT.

TABLE 1 Comparison of Expansile Forces of a Z-stent, a WALLSTENT and aNitinol Woven Stent Z W W Δ Z Z Side by W Over- Side by Woven (mm)Center Between Side Center lap Side Stent 2 16 13 19 15 35 18 44 4 36 2831 25 59 22 91 6 51 44 42 42 80 35 126 8 63 61 56 50 108 42 158 10 81 7962 60 126 48 167 12 100 98 76 74 149 54 175 14 115 119 90 84 170 63 18416 127 133 101 100 197 73 202 18 146 192 122 111 220 84 20 165 unmeasur.142 129 248 96

With respect to Table 1, the unit “g” for “grams” is used as a measureof force. Although the correct unit of force is the “dyne”, which isequal to the mass in grams multiplied by the gravitational constant, theinventors believe that the average reader will have a better idea aboutthe size of force when the associated mass unit (grams) is specified.

When one uses, e.g., a WALLSTENT or other commercially available stentfor stenting, the manufacturer usually recommends to use a stent one mmlarger than the diameter of the vessel, after precise determination ofthe size of the vessel, to eliminate the magnification factor caused bythe fluoroscopy/radiography. This minimal “overstenting” is used toachieve good contact between the stent and the vessel wall. Themanufacturer also typically provides exact data regarding therelationship between the stent's diameter and length to facilitateprecise positioning thereof. The woven nitinol design of the presentinvention has significantly greater expansile force than that of theWALLSTENT if a comparable number of wires are used to form the samecaliber stent (understanding that one wire as used herein and shown inFIG. 1C would require the use of two wires in the WALLSTENT, given thefree, unclosed wires thereof). Compared to the WALLSTENT, the closedstructures of the stents of the present invention and the better shapememory of the wires that may be used may result in a considerablereduction in the size of the wires used, in the number of wires used, aswell as in the angles between the wires. For instance, in small vesselapplications (e.g., coronary artery) it is advantageous to use theminimum amount of wire (metal) to reduce the possibility of thrombosisand/or restenosis. Furthermore, in preferred embodiments, angle a may bereduced below 90 degrees without losing the necessary expansile forcefor self anchoring. For the same vascular application, the same or evengreater expansile force can be achieved with a loosely-woven nitinoldesign of the present invention compared to the WALLSTENT and otheravailable stents. A stent of the present invention may also be chosen soas to have a diameter approximately ten percent larger than the diameterof the tubular structure to be stented.

Body 10 may also be formed from a single wire (“the single wireembodiment”). The single wire embodiment is illustrated in FIG. 1C,wherein wire ends 7 have not yet been twisted or coupled together toform a closed structure 4, as described below in greater detail. Oneversion of the single wire embodiment is illustrated in FIG. 50A. Asillustrated in FIG. 50A, body 10 of the stent has an axis 810, distalend 12 and proximal end 2. First segment 812 of wire 5 is separated fromsecond segment 814 by either bend 8 (not shown) or closed loop 6. Asshown in FIG. 50A, first segment 812 extends helically in a firstdirection around axis 810 toward end 2, and second segment 814 extendshelically in a second direction around axis 810 toward end 2. Firstsegment 812 crosses second segment 814 in a number of locations 816. Asshown in FIG. 50A, locations 816 define loops 818, which touch eachother such that the loops are contiguous. Loops 818 are “contiguous”because, with the exception of the first and last loops, each loopshares a point—location 816—with two other loops.

Segments 812 and 814 may be arranged in two different ways with respectto each other. As shown in FIG. 50A, segment 812 is positioned fartherfrom axis 810 than segment 814 at each location 816, while in FIG. 50B,segments 812 and 814 alternate being further from axis 810 at eachlocation 816. It will be understood to those of skill in the art, withthe benefit of this disclosure, that segment 812 may be positionedfarther from axis 810 than segment 814 at one or more locations 816.

In the single wire embodiment of the stents in FIGS. 50A and 50B, loops818 reside in a series of planes that includes two groups of planes (notshown), one of which includes the planes passing through the first,third, fifth, etc. loops 818, and the other of which includes the planespassing through the second, fourth, sixth, etc. loops 818. The planes ineach group are roughly parallel to each other. When body 10 is in itsunconstrained state, the planes in one of the groups intersect theplanes in the other group at acute angles falling within the range ofslightly greater than 0° to about 45°. Axis 810 passes generally throughthe center of each of loops 818.

As shown in FIG. 50C, certain of loops 818 of the single wire embodimentof body 10 of the stent may be separated by longitudinal segments inwhich segments 812 and 814 are twisted together. As shown, pairs ofcontiguous loops 818—with the exception of the loop located after closedloop 6—are separated by twisted segments 820. Although not shown, itwill be understood to those of skill in the art, with the benefit ofthis disclosure, that as many contiguous loops as are desired may beseparated by a twisted segment 820 from another loop or any other numberof contiguous loops to suit a particular application. For example, threecontiguous loops may be separated from another loop or two or more othercontiguous loops by a twisted segment in the same manner that the pairsof contiguous loops are separated by twisted segments as illustrated inFIG. 50C. Similarly, four contiguous loops may be separated from anotherloop or two or more other contiguous loops by a twisted segment. As yetanother example, a single wire embodiment stent may have only onetwisted segment separating two groups of five contiguous loops.

In contrast to the “hoop stent” disclosed in U.S. Pat. No. 5,830,229 toKonya et al. (“the hoop stent”), which is incorporated herein byreference, the single wire embodiment of the stent that has twistedsegments 820, depicted in FIG. 50C for example, possesses multiplecontiguous loops 818. As a result, the single wire embodiment stentswith such twisted segments are more resistant to forces compressingloops 818 in a lateral manner. The directions of such lateral forces areindicated by the large arrows in FIG. 50C. As a result, if the singlewire embodiment of the stent having multiple contiguous loops, such asthe stent depicted in FIG. 50C, is placed in a vessel or other structurethat is sometimes bent or flexed, that vessel or structure will morelikely remain patent when bent or flexed than it would were it supportedby the hoop stent.

Body 10 of a stent according to the present invention may be formed byvarious methods of plain weave including hand weaving and machineweaving. The following process is an exemplary embodiment of plainweaving according to the present invention. As shown in FIG. 16, atemplate 300 having a diameter corresponding to the chosen diameter ofbody 10 is provided. The top of the template is equipped with holes 302around its circumference. Pins 304 are placed through the holes suchthat they extend beyond the outer surface of the template on opposingsides. As shown in FIG. 16, wires 5 are bent at about their midpointaround the pins. This bending may result in the formation of bend 8 asshown, or wires 5 may be wrapped around the pins to form small loops 6(not shown). In one embodiment of body 10, angle b of small closed loop6 or bend 8 (FIG. 1A) may be less than 90°. In a more typical embodimentof body 10, angle b may be equal to or greater than 90°, and mayapproach, but not include, 180°. In an even more typical embodiment,angle b may be about 140-160°. As discussed above, bends 8 and loops 6are created in a manner that makes them likely more mechanically soundthan the joints disclosed in the Wallsten patent created by connectingtwo wire ends together through welding or gluing.

In one embodiment of the present plain weaving process, the ends of twowires 5 may be coupled together and placed around pin 304, instead ofbending a single wire 5 as above described. This coupling may beachieved by using any suitable means capable of preventing the wiresfrom returning to their straight, unbent configuration. As shown in FIG.30A, such means include bending and crimping a metal clip around thewires. In another embodiment of the present plain weaving process, asshown in FIG. 30B, two wires 5 may each be wrapped around pin 304separately and secured using any suitable means, such as those justdescribed, in further contrast to bending one wire around pin 304. Afterannealing (i.e., heating and cooling) wires 5 shown in FIG. 30B asdescribed below, the two wires may be coupled to each other using anysuitable means such as twisting, crimping or tying as further belowdescribed.

Although only two pins are shown in FIG. 16, it is to be understood thatthis is done for illustrative purposes only, and not to indicate theappropriate number of wires to use in any given application. In anexemplary embodiment, template 300 is typically formed of brass orcopper, but may be formed of any suitable material capable ofwithstanding the cure temperature below discussed, such as stainlesssteel. Similarly, in an exemplary embodiment, pins 304 are typicallyformed of stainless steel, but may be formed of any similarly suitablematerial. It is to be understood that the pins may be supported by thetemplate by any suitable means capable of withstanding the curetemperature, including preforming, attachment by welding, threading, orthe like.

As shown in FIG. 17, after the wires have been bent around the pins, thewires are secured to the template to prevent them from returning totheir original, straight, unbent position. This may be necessary giventhe superelastic nature of wires such as nitinol and the like (discussedbelow). As shown in FIG. 17, wires 5 are secured by securing wire 306around the outside of wires 5 so as to secure wires 5 against theoutside of the template. In an exemplary embodiment, copper is typicallyused for securing wire 306, but it is to be understood that any suitablewire capable of withstanding the annealing temperature of about 500° C.discussed below may be used. After the wires are secured, small weights360 (shown in FIG. 20) are attached to the free ends of the wires usingany suitable means such as tying, or the like. In an exemplaryembodiment, weights with masses of approximately 50-100 grams maytypically be used with wires having diameters of between about 0.005inches and about 0.011 inches. However, it is to be understood thatweights of different masses may be chosen so long as the wires are keptunder tension (i.e. straight) during plain weaving (as described below),and properly balance the central weight (described below).

As shown in FIG. 18, a stand 330 with a circular plate 320 is providedwith an opening 325. The diameter of the opening may depend on thediameter of the template. In an exemplary embodiment, an opening with adiameter of about 4.5 cm may be typically utilized in conjunction with atemplate of about 1.0 cm. It is to be understood, however, that anopening with a diameter more closely corresponding to the diameter ofthe template may be utilized.

As shown in FIG. 19, before or after the weights are attached to theends of wires 5, the template is inverted. In an exemplary embodiment,the weights may be typically attached to the free ends of the wiresprior to inversion of the template such that the wires are kept undertension and may be prevented from returning to their unbent, nominalstate. A central weight 340 may then be attached to the end of thetemplate. In an exemplary embodiment, the central weight may betypically hung from the pins. However, it is to be understood that thecentral weight may be attached to the template's end in any suitablemanner, such as hanging from holes in the template itself, etc.

Before or after central weight 340 is attached to the end of thetemplate, the inverted template is placed through opening 325, as shownin FIG. 20. In an exemplary embodiment, the central weight may typicallybe attached to the inverted template after the inverted template isplaced through opening 325. As shown in FIG. 20, the wires 5 may bearranged fairly evenly around the circumference of the circular plate.As shown in FIG. 21, in an exemplary embodiment of the presentinvention, 6 wires having 12 ends numbered 1-12 (each wire having 2ends) are shown as being arranged in a substantially symmetrical fashionaround circular plate 320. The weights 340 and 360 typically serve tokeep the wires under tension and in balance. Next, the plain weaving maytake place.

In the manner shown in FIG. 22, the weave may be started by crossing onewire end over the adjacent wire end. This crossing may be made in eithera clockwise or counterclockwise fashion. This crossing may be carriedout as directed by the arrows shown in FIG. 22. After a complete set ofcrosses (or one “turn”) has been carried out, the location of thecrossed wire ends is as shown in FIG. 23. In an exemplary embodiment,the resulting location of the wire ends may be achieved by crossing onewire end over another in one direction while slightly shifting the wireend not crossed in the opposite direction. In an exemplary embodiment,this shifting may be about 15°. Thus, wire end 1 may be crossed in aclockwise direction over wire end 2, while shifting wire end 2 about 15°counterclockwise. Once one turn has taken place, crossing may begin inthe same fashion, but in the opposite direction, as shown in FIG. 24.This process may be repeated until the plain weave is complete.

The tightness of the plain weave (i.e., the angle a between thewires—FIG. 1A) may be adjusted by changing the central weight. Anincrease in the central weight results in a looser weave (decreasedangle a between the wires) and vice versa. Upon completion of the plainweave, the adjacent wire ends may be closed as below described.

In an exemplary embodiment according to the present invention, aconventional braiding machine may be utilized to arrange wires 5 in aplain weave to form body 10 of a stent or any other device describedherein. Such a braiding machine may be obtained, for example, fromWardwell Braiding Machine Company in Central Falls, R.I. The manner inwhich a plain weave may be achieved using a conventional braidingmachine is displayed in FIG. 7 of U.S. Pat. No. 5,419,231 to Earle, IIIet al. (1995), which is hereby expressly incorporated by reference, aswell as in FIG. 1 of U.S. Pat. No. 5,485,774 to Osborne (1996), which ishereby expressly incorporated by reference.

After the plain weave process is complete, as shown in FIG. 1A, at therear or proximal end 2 (the end closest to the surgeon/operator) of body10, wire ends 7 may be twisted together using multiple twists so as toform closed structures 4. In an exemplary embodiment, as few as 2 twistsmay be used, and as many as about 6. In an exemplary embodiment, it ispreferable to keep the twisted wire ends as short as possible. Theshorter the twisted wire ends are kept, the more resistant to bendingthe twisted wire ends are. As a result, the twisted wire ends are lesslikely to be inadvertently displaced during placement, repositioning, orretrieval, thus reducing the potential for causing tissue damage.Although not shown, it will be understood to those of ordinary skill inthe art with the benefit of the present disclosure that the wire endsmay be coupled together, instead of by twisting, using any suitablemeans capable of withstanding the heating described below, such asbending and crimping a metal clip around the wires, tying them togetherwith suitable material such as stainless steel wire, welding, etc.

Other configurations of template 300 may also be utilized consistentlywith the present disclosure. For example, template 300 may be providednot only with pins 304 or tabs 600 (described below), around which wires5 are bent, wrapped, tied, twisted, etc., prior to weaving the body ofthe stent (or the bodies of any of the woven structures disclosedherein), but may also be provided with pins around which the wire endsmay be twisted in fashioning closed structures 4. Finish pins 800 may besupplied on a ring, such as ring 802 depicted in FIG. 48, in anysuitable fashion, including, for example, through removable or permanentattachment. Ring 802 may be configured to threadably engage template 300as depicted in FIG. 48. In other embodiments, ring 802 may be configuredto engage template 300 by virtue of frictional forces (not shown) or maybe configured to be secured to template 300 as would a clamp (notshown). Finish pins 800 may also be engaged with template 300 in thesame manner as pins 304. As shown in FIG. 49, in such an embodiment,template 300 may be provided with finish holes 804 similar to holes 302,and finish pins 800 may be placed through finish holes 804. Ring 802 mayalso be utilized in place of holes 302 and pins 304.

In an embodiment in which finish pins 800 are engaged with template 300through the utilization of ring 802, the number of finish pins utilizedmay be equal to the number of wires 5 that are used. Template 300 may bethreaded along any portion of its length so as to best accommodate avariety of woven body sizes. For example, only a portion of template 300may be threaded, as depicted in FIG. 49. Threads need not be utilizedwith a ring that engages template 300 by virtue of frictional forces.

Advantageously, the use of ring 802 allows for the easy and precisealignment of pins 304 or tabs 600 with finish pins 800. Anotheradvantage afforded by the use of ring 802 is the ease with which theprecise length of the woven body may be achieved. The length of thewoven body may be achieved by adjusting and fixing the distance alongthe length of template 300 between pins 304 or tabs 600 and finish pins800. In an embodiment in which finish pins 800 are placed through finishholes 804, the number of finish pins utilized may be equal to one-halfof the number of wires 5 that are used, since both ends of the finishpins will be utilized. Template 300 may be provided with finish holes804 along any portion of its length so as to best accommodate a varietyof woven body sizes. For example, only a portion of template 300 may beprovided with finish holes 804, as depicted in FIG. 49.

As with ring 802, the use of finish holes 804 advantageously allows forthe easy and precise alignment of pins 304 or tabs 600 with finish pins800. Additionally, the precise length of the woven body mayadvantageously be achieved by virtue of the distance along the length oftemplate 300 between pins 304 or tabs 600 and finish holes 804 (and,therefore, finish pins 800.)

With finish pins 800 in place, once the wire ends of wire(s) 5 have beenwoven around template 300, the wire ends may be secured around finishpins 800 in any suitable manner to form closed structures 4, includingby twisting, bending, wrapping and the like. In one embodiment, the wireends may be crossed, then bent around finish pins 800 and then securedtogether using a short piece of a thin-walled metal tubing. Such a jointmay then be reinforced by soldering, welding, or the like. A suitablenumber of additional twists may be utilized after securing the wire endsaround finish pins 800 in forming closed structures 4. Securing wire 306(not shown) may be utilized to secure closed structures 4 to template300 during annealing.

As a result of securing the wire ends around finish pins 800, the anglecreated between the crossed wire ends may be similar, if not identicalto, angle b described above. Advantageously, by using finish pins 800,this angle between the crossed wire ends may be maintained, preventingthe weave of the woven body from loosening. Were loosening to occur, theexpansile or radial force of the portion of the body with the loosenedweave could decrease, causing that portion of the woven body to remainelongated within the structure in which it is placed. Therefore, throughthe use of finish pins 800 and as a result of the correlatingmaintenance of the angle between the crossed wire ends that are wrappedor twisted around the finish pins, the tightness of the weave along thelength of the woven body—from end to end—may be consistent and resistantto loosening, and the expansile force of the end of the woven bodyhaving closed structures 4 may be comparable to the expansile force ofthe other portions of the woven body.

Another method of creating body 10 of a stent according to the presentinvention is illustrated in FIGS. 37-47B. As shown in FIG. 37, the baseof template 300 may be equipped with longitudinal tabs 600 formed by twolongitudinal cuts connected by a transverse cut. The length of the cutsmay be determined based upon the size of the template chosen. Forexample, a template that is about 10 mm in diameter may havelongitudinal tabs with longitudinal cuts about 4 to 5 mm long, and theconnecting transverse cuts may be about 2 mm long. As illustrated inFIG. 37, tabs 600 may be slightly elevated from the surface of template300 and may be positioned equally around template 300.

FIGS. 37 and 38A and B also illustrate that wires 5 may be bent aroundtabs 600 at selected points located between the ends of the wires toform bent portions along wires 5. The bent portions may take the form ofbends 8, as shown in FIG. 38A, or may be further wrapped around tabs 600to form loops 6, as shown in FIG. 38B. Angle b of bends 8 or loops 6 maybe less than 90°. In a more typical embodiment of body 10, angle b maybe equal to or greater than 90°, and may approach but not include, 180°.The bent portions may be arranged to define end 12 of body 10. Wire ends7 of wires 5 may then be weaved to create body 10 using, for example,the following machine weave method.

As shown in FIG. 39, ends 7 of each wire 5 may be arranged around a pairof bobbins 602. The length of the wire wound around each bobbin may bedetermined by considering the total length of the wire needed to formbody 10 as well as the wire length needed to arrange the bobbins aroundweaving plates (shown in FIG. 40), which are discussed below in greaterdetail.

As shown in FIG. 40, in one embodiment in which bobbins 602 areutilized, two coaxially arranged weaving plates may be utilized. Asshown in FIG. 41, upper weaving plate 604 and lower weaving plate 606may be positioned in different horizontal planes. FIG. 41 illustratesthat the weaving plates may be equipped with multiple bobbin rods 608,the axes of which are substantially perpendicular to the weaving plates,on which bobbins 602 may be slidably secured. (FIG. 41 depicts only 4bobbins for the sake of simplicity.) The weaving plates may be providedwith holes therein through which template 300 and/or wires 5 may pass,as shown in FIG. 41. Template 300 may be secured to the base of theweaving machine chosen using any suitable means such as template rod610, around which template 300 may pass, as shown in FIG. 41. Template300 may be secured to the base of the weaving machine chosen using anysuitable means such as template rod 610, around which template 300 maybe slidably placed (FIG. 35). Template rod 610 may be configured tofirmly engage template 300 through frictional forces (e.g., by taperingtemplate rod 610). Instead of template rod 610, any appropriate lockmechanism may be used to secure the base of the weaving machine totemplate 300.

As shown in FIGS. 42A and 43A, the pairs of bobbins 602 may be preparedfor weaving by arranging one bobbin on upper weaving plate 604 and theother bobbin from the pair on lower weaving plate 606. Wires 5 may thenbe bent around tabs 600, and the ends of the wires may be attached tobobbins 602 using any suitable means capable of holding wires 5 undertension throughout the weaving process. An example of such a mechanismis a one-way brake that allows bobbin 602 to rotate in a singledirection only, such that the wire 5 may wind off bobbin 602.Simultaneously, such a brake may be configured so as to continuouslymaintain tension in wire 5 by virtue of the brake's resistance to thewinding off of wire 5.

As shown in FIG. 42A, with the wire ends in place, the weaving may beginby crossing the wire ends of the same wire, which results in theformation of a small caliber loop 6 (FIG. 42B) at the site of the bentportion. In another manner of weaving illustrated in FIG. 43, the wireends of different wires may be crossed first, resulting in bend 8 at thesite of the bent portion (FIG. 43B).

As shown in FIGS. 44-45, the two weaving plates may be arranged suchthat the surfaces thereof from which the bobbin rods extend face eachother. In this alternative embodiment, the diameters of the plates maybe the same or different. Wires 5 may be arranged on bobbins 602 in thesame manner as described above, as shown in FIG. 45.

Despite which of the aforementioned weaving plate arrangements isutilized, the weaving plates rotate in opposite directions during theweaving process. The weaving plates may be operated at any suitablespeed. In this regard, a speed as low as 1 to 10 cycles per minute isacceptable. The weaving plates may also be driven by hand.

The weaving plates may supported and rotated using any suitable means.FIG. 61 illustrates one means of supporting and rotating weaving plates604 and 606. (FIG. 61 depicts on 4 bobbins for the sake of simplicity.)As shown, weaving plate supporter 650 may be equipped with lower arm 652and upper arm 654 for supporting lower and upper weaving plates 606 and604, respectively. Weaving plate drivers 660 may be secured to the upperand lower arms of the weaving plate supporter and engaged with theweaving plates in order to operate them. The drivers may be configuredto operate in any suitable fashion. For example, the drivers may beconfigured with a power source and provided with gears of any suitableconfiguration for causing the weaving plates to rotate. The drivers mayalso be configured to utilize magnetism or electromagnetism to rotatethe weaving plates. The drivers may be also be configured such that theweaving plates may be rotated by hand. Further, although not shown, itwill be understood to those of skill in the art, with the benefit ofthis disclosure, that either or both of the upper and lower arms may beprovided with branches to which drivers may be attached. The drivers onthe branches could then be secured to or engaged with the top surfacesof the weaving plates in the same fashion that drivers 660 are engagedwith the bottom surfaces of the weaving plates as shown in FIG. 61.Thus, in such an embodiment, both the top and bottom surfaces of eachweaving plate would be engaged with drivers.

A braiding machine suitable for carrying the weaving process justdescribed (i.e., utilizing the weaving plates) may be obtained, forexample, from Wardwell Braiding Machine Company in Central Falls, R.I.

After the weaving process is complete, wire ends 7 may be twistedtogether or coupled as described above to form closed structures 4. Tomake the process of wire twisting faster and easier, the wires may betwisted with a special hand tool designed for this purpose. Tool 612illustrated in FIG. 46A follows the principle of an automatic pencil.Jaws 614 of tool 612 are configured so that wire ends 7 may be firmlyheld between jaws 614. Jaws 614 may be activated by push button 616moving against spring 618. After placing wire ends 7 into pre-formedgaps 620 located between jaws 614 (FIG. 46B), spring 618 expands (orreturns to its unconstrained state) and retracts jaws 614, securing wireends 7 firmly between jaws 614 due to the pressure of outer housing 622acting to close jaws 614. Outer housing 622 may then be rotated tocreate multiple twists of wire ends 7. As illustrated in FIGS. 47A and47B, the twisted ends of body 10 may be secured to template 300 usingtransverse tabs 624, which may be formed the same way as longitudinaltabs 600.

Turning to the single wire embodiment, body 10 may be formed usingeither the hand weaving process or the machine weaving process, both ofwhich are described above. In preparation for the weaving process,template 300, which may be configured to have any suitable shape, may beprovided with pin 304 or longitudinal tab 600 near the end thereof atwhich the weaving is to begin. Near its other end, template 300 may beprovided with finish pin 800 or transverse tab 624, which may beappropriately aligned with pin 304 or longitudinal tab 600. In oneembodiment, finish pin 800 may be provided on ring 802.

The weave of body 10 may then be started by bending wire 5 around pin304 or longitudinal tab 600 to form either bend 8 or closed loop 6. Inan exemplary embodiment, securing wire 306 may be utilized to securebent wire 5 to template 300 as described above. The two segments of wire5 on either side of bend 8 or closed loop 6 may then be woven to createbody 10 by helically wrapping the segments around template 300 inopposite directions toward finish pin 800 or transverse tab 624. Thesegments may be crossed over each other during the process inalternating fashion to result in the single wire embodiment depicted inFIG. 50B. This weaving may take place either by hand or using theweaving templates described above.

After the weaving is complete, in one embodiment, closed structure 4 maybe created by wrapping the wire ends around finish pin 800 in the mannerdescribed above. In another embodiment, the wire ends may be twisted orcoupled together as described above to form closed structure 4, whichmay then be secured to transverse tab 624. It will be understood thatadditional pins 304 or longitudinal tabs 600 may be utilized to createthe single wire embodiment. Such additional pin(s) or tab(s) may bevertically aligned with the other pin or longitudinal tab such thatmultiple closed loops 6 may be formed at the end of body 10 where theweave begins, as depicted in FIG. 50B. Similarly, additional finish pinsor transverse tabs may be utilized in the same fashion. The use ofpin(s) 304 or longitudinal tab(s) 600 with finish pin 800 or transversetab 624 will advantageously ensure that wire 5 remains in positionduring annealing. The annealing processes described below may beutilized for annealing the single wire embodiment.

After the plain weave of wires 5 is completed on the template, if thewires are made of a material that can be programmed with either thermalshape memory or superelasticity such as nitinol or other shape memorymaterials described below, body 10/template unit may be heated so as toprogram body 10 with either thermal shape memory or superelasticity. Ifbody 10 is programmed with superelasticity, its initial shape can bedeformed by applying a force thereto. After removal of the force, body10 may substantially recover its initial shape. If body 10 is programmedwith thermal shape memory, its initial shape can be deformed uponapplication of a force at a first temperature. The force may be removed,and body 10 may remain deformed until heated to a second temperature. Atthe second temperature, body 10 may substantially recover its initialshape.

In programming body 10 with superelasticity, the body 10/template unitmay be heated to about 500° C. for about 5 to 15 minutes, typicallyabout 12 to 15 minutes, and even more typically for about 15 minutes, inan oven. After allowing the unit to cool to room temperature, wires 5possess superelastic properties. In an exemplary embodiment, naturalcooling is typically used. It is to be understood, however, thataccelerated cooling using a fluid bath, for example, may be utilizedresulting in slightly different superelastic characteristics than areachieved with natural cooling. In programming body 10 with thermal shapememory, the body 10/template unit may be heated to about 500° C. forabout 60 to 120 minutes, typically about 120 minutes, in an oven. Afterallowing the unit to cool to room temperature, wires 5 possess thermalshape memory. In an exemplary embodiment, natural cooling is typicallyused. It is to be understood, however, that accelerated cooling using afluid bath, for example, may be utilized resulting in slightly differentthermal shape memory characteristics than are achieved with naturalcooling.

In an exemplary embodiment of body 10, it is preferable to furtherreinforce the coupled wire ends of closed structures 4 after body 10 hasbeen properly annealed (especially if twisting was utilized). Thisreinforcement may be accomplished by any suitable means such as pointwelding, soldering, pressure welding, or the like. The wire ends ofclosed structures 4 may be soldered by removing any oxide layer that mayhave formed over the relevant portions of the wires used, and applyingsolder to those portions. Soldering may be enhanced by first wrappingthe coupled wire ends of the closed structures 4 with thin stainlesssteel wires. In an exemplary embodiment, point welding is preferred tosoldering, because point welding is easier to perform than soldering,and may be more suitable with regard to long-term implantation of thestent.

The wires of body 10 may be constructed of any material compatible withthe tissue in which the stent will be placed. Further, the material maybe suitably rigid and elastic and capable of being programmed witheither superelasticity or thermal shape memory. The materials may, forexample, be NiTi alloys like nitinol. Such alloys can be heated andallowed to cool to room temperature, resulting in the alloys havingeither superelastic or thermal shape memory properties, depending on theheating time as above described. Other alloys that may be used includeFePt, FePd, and FeNiCoTi. These alloys may be heat treated to exhibitthermoelastic martensitic transformation, and, therefore, good thermalshape memory. Other alloys such as FeNiC, FeMnSi, and FeMnSiCrNi do notpossess long-range order and undergo nonthermoelastic transformation,and, thus, may also be used. Additionally, some β-Ti alloys andiron-based alloys may also be used.

In an exemplary embodiment, nitinol possessing about 55 to 56% Nickel,and 45 to 44% Titanium, may be used for wires 5 of body 10. Such nitinolwires are commercially available from Shape Memory Applications in SantaClara, Calif.

When using nitinol wire, the radiopacity of body 10 advantageouslyincreases over the radiopacity of stents formed using materials such asstainless steel. The radiopacity depends primarily on the diameter ofthe nitinol wires and the tightness of the plain weave created by thewires. The radiopacity of body 10 can be increased further by usingsilver solder to reinforce the coupled wire ends forming closedstructures 4.

The wire sizes that may be used for the stents of the present inventionvary depending on the application of the stent. In an exemplaryembodiment, small stents ranging from about 2 to about 4 mm in diameterand about 1 to about 2.5 cm in length, typically for coronaryapplication, may utilize wires from about 0.003 to about 0.006 inches indiameter. In an exemplary embodiment, medium stents ranging from about4.5 to about 10 mm in diameter and about 2 to about 10 cm in length,such as are used in the iliac artery, femoro-popliteal artery, carotidartery, and the renal artery, may utilize wires from about 0.006 toabout 0.009 inches in diameter. In an exemplary embodiment, large stentsabove about 10 mm in diameter may utilize wires from about 0.006 toabout 0.012 inches in diameter. Applications for the large stentsinclude the aorta (typically a vessel diameter in about the 20 to 40 mmrange), the inferior vena cava (“IVC”), which is usually less than about28 mm in diameter, the superior vena cava (“SVC”), the esophageal (20-25mm in diameter), and the colon, which may be about 15 to about 25 mm.

Tapered Stents

With reference to the illustrative embodiment shown in FIG. 14, there isshown a tapered stent for insertion and delivery into an anatomicalstructure. Tapered body 100 may be formed using plain weave by themethods above described. Potential embodiments of tapered body 100include the single wire embodiment. The types of applications for whicha tapered stent may be used include the ilio-femoral, femoro-poplitealarteries, as well as in the carotid arteries for stenting long lesions.

The tapered configuration may be achieved different ways. In a firstmethod using the hand weave method or any of the machine methodsdescribed above, a template may be chosen possessing an appropriatetaper. In an exemplary embodiment, a template with a smooth,contiguously decreasing diameter without steps is typically used. Theshape of the template may correspond roughly to the inner shape of thetapered stent. The shape of the tapered stent may be chosen based on theshape of the vessel or structure into which it will be placed.

In an exemplary embodiment, it may be preferable to choose a shape forthe tapered stent (and, thus, for the template) such that a“wedge-effect” will be achieved between the tapered stent and the vesselor structure into which it is placed. The wedge-effect may be used tofix the stent in position and prevent it from distal migration. It is tobe understood, however, that any suitable means for improving thefixation of the stent in the vessel or structure, such as flaring theproximal end of the stent, may be used in addition to or instead of thewedge-effect.

Using such a template and either hand or machine weave, the weave may besubstantially uniform along the axial length of the stent. As a resultof the substantially uniform weave, the expansile force of the stent maybe substantially uniform along the axial length of the stent. Althoughthe expansile force may be substantially uniform as stated, the matchbetween the diameters of the tapered stent and the vessel into which thestent is placed may result in the vessel being exposed to a force lesserthan would be exhibited by a straight stent.

In another embodiment according to the present invention, a templatepossessing a uniform diameter as described above may be chosen for usewith either the hand weave method or a machine method. The diameter ofthis template may correspond to the diameter of the largest portion ofthe stent. Tapered body 100 may be woven around this template and heatedand cooled as above described. The wire ends of closed structures 104may then be reinforced as needed for the application. Tapered body 100may then be mounted on a tapered template in a fashion similar to theone described above (e.g., using a copper wire), and reheated in amanner similar to the original heating. Forming the stent in this mannerresults in a contiguously loosening mesh toward the tapered end of thestent. That is, angle a is contiguously decreased toward the distal end102 of tapered body 100 resulting in a decreasing expansile force of thetapered stent towards the tapered distal end 102.

It is to be understood that if a stent (or any other device disclosedherein) is remodeled a number of times and it is not intended that thestent be programmed with thermal shape memory, care should be taken notto exceed a total heating time (which includes the first heating timeand the second heating time, etc.) of about 60 minutes, because at about60 minutes, the stent may be programmed with thermal shape memory.

As with body 10, one or more of the coupled wire ends of tapered body100 may be left slightly longer than the others and bent inward so as toallow for retrieval of the stent using a foreign body retrieval device.Further, closed structures 104 of body 100 may be flared to improvestent fixation.

In an in vitro study, the expansile force of the tapered stent of thepresent invention was found to be proportional to the weave tightness.The results of this study are set forth below in Table 2. The tightnessof the weave is strongly associated with the angle between the crossingwires as well as with the number of wires used for creating the weave.The stents used in the study were built from 0.011 inch nitinol wires.If the angles between the crossing wires are wide (closer to 180°), thestent is better able to withstand any outer compression. An increase inthe diameter of the nitinol wire would increase the expansile force ofthe stent.

TABLE 2 Taper-Shaped Self-Expanding Repositionable Stent ComparativeStudy, Using 0.011″ Diameter Wires 10 Wires, 8 Wires, 6 Wires, 6 Wires,Δ Tight Moderate Loose Tight (mm) Weave Weave Weave Weave 2 115 91 26 924 176 123 55 103 6 208 141 74 119 8 238 158 92 126 10 273 170 103 136 12293 186 120 145 14 331 202 129 153 16 371 223 146 171

With respect to Table 2, the inventors used the unit “g” for “grams” asthe measure of force for the reasons discussed above. Similarly, thedesignation Δ in the leftmost column of Table 2 represents thecircumferential displacement (in mm) of the stent in question. Forexample, a Δ of 2 mm indicates that the circumference of the stent inquestion was reduced by 2 mm, and the force necessary to effect thatdisplacement was then recorded.

Advantages of the tapered stent of the present invention include superbflexibility, repositionability and removability, precisepositionability, and better matching than a cylindrical stent with auniform diameter between the tapered vessel and the stent which mayresult in less intimal reaction and longer vessel patency.

Covered Stents

Various material may be suitably used as grafts (including materialsused as covers and those used as liners) that may be attached to thepresent woven stents so as to create stent grafts. One type of coveringmaterial that may be utilized for this purpose is made from materialthat is stretchable enough to substantially follow the movement of thestent's mesh. This type of graft material includes woven polyester,Dacron, polyurethane and the like. Depending on the application, thegraft material may, for example, be somewhat porous (to facilitateendothelial ingrowth), highly porous (to leave bridged side branchespatent) or non-porous (e.g., to exclude an aneurysm or fistula fromcirculation, or in another application to prevent tumor ingrowth intothe stent graft lumen).

The graft material may be attached to either the outer or the innersurface of the stent, so as to serve as a cover or a liner,respectively. The graft material may be attached to the stent usingmonofilament sutures (e.g., polypropylene such as 5-0, 6-0, 7-0 Prolene,which is commercially available from Ethicon), glue, heat, or any otherappropriate means.

Graft materials that are not stretchable or elastic may also be utilizedto form stent grafts. One such material is PTFE. Such graft material maybe attached to only one of the stent end's, thereby allowing freemovement of the wire mesh. The attachment between the stent and thegraft material may be created at the proximal end of the resulting stentgraft (that is, the end of the stent that will be closest to theoperator).

Such a stent graft may be pre-loaded into an appropriately-sized sheath.The graft material may be folded or arranged so that it occupies aslittle space within the sheath as possible.

Delivering a stent graft having a graft material made from a relativelynon-stretchable material such as PTFE may be performed in a manner thatis different than the manner in which a stent graft having a stretchablegraft material may be delivered. For example, with a stent graft havinga cover made from relatively non-stretchable graft material, after thestent graft is positioned as described below in greater detail, thesheath may be retracted and the graft material may thereby be exposed.Then the stent may be allowed to assume its unconstrained diameter byusing the coaxial delivery system. The fact, that the coaxial deliverysystem enables to achieve a more compressed mesh tightness than thatachievable by allowing the stent to recover, may be advantageous tocreate an adequate contact between both the stent and the graft as wellas between the stent graft and the vessel wall. The different deliverymechanism requires a different approach to stent graft retrieval. First,the stent is completely restretched over the delivery tubes and thestent's completely elongated position is secured by the proximal lockmechanism. Second, the sheath is advanced preferably using some rotatingmovement to recapture the graft material. The creation of the attachmentsite between the stent and the graft at the proximal end of the stent isadvantageous for possible repositioning. The stent's proximal end issecured to the outer delivery tubes, and the graft to the proximal endof the stent, therefore, the proximal portion of the graft is formedinto a funnel shape facilitating its retrieval into the sheath.

Side-By-Side Stent Placement in Aorta and Bilateral Renal Artery

The present stents may be delivered in a variety of anatomicalstructures. Further, they may be used in conjunction with each other ina variety of manners to best treat the diseased structure. For example,as shown in FIG. 54, the bilateral aorto-renal junction 830, consistingof aorta 832, left renal artery 834 and right renal artery 836, alongwith the aorto-iliac junction 840, consisting of left iliac artery 842and right iliac artery 844, may be treated using uses two stentspositioned in side-by-side relationship with each other. Alternatively,stent grafts shorter in length than those shown in FIG. 54 may bedelivered within the aorta or the aorto-iliac junctions with someoverlap therebetween.

The stents that may be utilized may be woven and annealed as describedabove on a variety of templates. In one embodiment, straight templatesmay be used. The stents may also be woven and annealed as describedabove so as to be relatively tapered, such as those in FIG. 54. In sucha configuration, the portions of the stents that will occupy the aortamay be larger in caliber than those portions of the stents that willoccupy the renal arteries. The stents may also be woven on templatesthat are configured with a bend that may approximate or match the anglebetween the appropriate renal artery and the aorta.

Stents that may be partially or completely provided (i.e., covered orlined) with any of the graft materials described above using any of themethods of connection described above may be used in this application.In the embodiment of the pair of stents illustrated in FIG. 55, theportions of the stents that occupy aorta 832 and portions of the stentsproximate the caudad surfaces 838 of renal arteries 834 and 836 arecovered. By only partially covering the portions of the stents that willoccupy renal arteries 834 and 836, the possibility of endoleak from therenal arteries may be greatly reduced or eliminated.

In another possible embodiment suitable for this application illustratedin FIG. 56, the aorto-renal stent may include struts 850 that may beformed by twisting neighboring segments of wires 5 during the weavingprocess. Struts 850 may also be formed in any suitable manner such as byencasing neighboring segments of wires 5 in flexible tubes, such asthose made of nitinol, or by soldering or welding neighboring segmentsof wires 5 together, etc. As used herein, “struts” means segments ofwires that are joined together in any suitable manner such as twisting,encasing within a sufficiently flexible piece of tubing, soldering,welding, etc., such that the portion of the stent formed from the strutsis less disruptive of the blood flow therethrough than would be the sameportion formed from a weave. The stent graft having struts 850 may, likethe stent grafts depicted in FIG. 55, be covered partially with anysuitable graft material, such as those relatively stretchable materialsdisclosed above. Accordingly, the portions surrounding struts 850 may becovered while leaving struts 850 uncovered and therefore arranged sothat when delivered as shown in FIG. 56, struts 850 are advantageouslypositioned within the vasculature with regard to hemodynamics. The useof struts 850 in this fashion may be advantageous in comparison toleaving a similar portion of the stent utilized simply bare, as in FIG.55, in that struts 850 would be less likely to create turbulence in theblood flow.

In one embodiment of the stent graft illustrated in FIG. 56 havingstruts 850, different portions of the stent may be provided withdifferent numbers of wires. Turning to such a stent, the weave may beginat the end of the stent that will be placed in the renal artery and madebe made from n wires. The portion of the stent occupied by struts 850may also be made from n wires. The larger portion of the stent that willoccupy the aorta may use n+x wires, where x denotes the number ofadditional wires utilized, and may be between 1 and 2n. Preferably, x isselected from an integer between 2 and n, and more preferably x equalsn. The template on which this type of stent is formed may have pins 304positioned, for example, at locations proximate the end and beginning ofstruts 850.

Biodegradable Devices

Both the straight and the tapered stents of the present invention (aswell as the filters and occluders discussed below), except for thesingle wire embodiments of these devices, may be formed with filamentsmade of biodegradable material so as to form self-expanding,bioabsorbable, biodegradable stents that may, in addition to functioningas stents, function as drug or nutrient delivery systems as a result ofthe material used.

Many factors may be considered in choosing materials from which to formthe biodegradable stents of the present invention. In one embodiment,the biodegradable stents of the present invention may be formed frommaterials of minimal thickness so as to minimize blood flow blockage andfacilitate bioabsorbtion. In another embodiment, the material may bechosen so as to exhibit sufficient radial strength to allow the bodyformed to function as a stent. The material from which the biodegradablestents may be formed may also degrade within the bloodstream over aperiod of weeks or months, so as not to form emboli. The material may bechosen such that the stent does not degrade before an endothelial layerforms in the stented vessel or structure in cases in which stenosedaortoiliac arteries with lengthy affected segments are treated. Thematerial chosen may be chosen to be compatible with surrounding tissuein the vessel as well as with blood.

The body of a biodegradable stent may be formed by plain weave using themethods above described. The size of the filaments used may varyaccording to the application. In some embodiments, the filaments may bereduced in size in comparison to the size of wires used in comparableapplications involving non-biodegradable devices. In other embodiments,the number of filaments used may be increased in comparison to thenumber of wires used in comparable applications involvingnon-biodegradable devices.

The minimum number of filaments that may be used to create the body of abiodegradable device (including stents, occluders and filters) may beabout 5. In one embodiment, 12 filaments may be used. With regard tostents, in creating the body using plain weave, the angle of the crossedfilaments (described above as angle a) may vary as described above, butis typically 150-160°. In one embodiment, the angle of the crossedfilaments may be as large as possible to achieve the largest radialforce possible and further ensure that the stent may have enoughexpansile force to remain in place after being delivered. The filamentends, after plain weaving is complete, may be coupled together to formclosed structures using any suitable means such as by heat treatment orsealing, gluing, tying, twisting, crimping, taping, or the like. Inanother embodiment, a long body may be woven, and the body may be cutinto tubular segments. Closed structures may be formed at both ends ofthe segmented bodies by coupling the filament ends together as abovedescribed.

In one embodiment, the filaments used may be made of polyglycolic acid(“PGA”), poly-L-lactic acid (“L-PLA”), polyorthoesters, polyanhydrides,polyiminocarbonates, or inorganic phosphates. These polymers arecommercially available from United States Surgical Corporation, Norwalk,Conn.; Birmingham Polymers, Inc., Birmingham, Ala.; and Ethicon,Sommerville, N.J., for example. One factor to consider in choosing amaterial from which to make the filament will be the goal of the stentplacement. For example, in an embodiment in which the stent servesmainly as a drug delivery system, PLA may be used because of its rapiddegradation time. In another embodiment in which the stent serves mainlyto maintain the patency of the vessel (i.e., keeping the vessel open)and as a scaffold or frame for the development of a new endotheliallayer, PGA may be used considering its high strength and stiffness. Inother embodiments, glycolide may be copolymerized with other monomers toreduce the stiffness of the resulting fibers that may be used.

In another embodiment, any of these filaments may be provided with about0.05 to 0.25 percent by weight of a basic metal compound, such ascalcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate,magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesiumphosphate, sodium phosphate, potassium sulfate or the like, to increasethe in vivo strength retention of the biodegradable stent by about tento twenty percent or more, as described in U.S. Pat. No. 5,478,355 toMuth et al. (1995), which is hereby expressly incorporated by reference.As used herein, “in vivo strength retention” refers to the ability of abiodegradable body to retain its strength (i.e., the breaking load ofthe body) after being implanted or delivered into a living creature. Inyet another embodiment, a filament obtained from a polymer containingabout 15 to about 30 mole percent glycolide in a melt spinningoperation, as described in U.S. Pat. No. 5,425,984 to Kennedy et al.(1995), which is hereby expressly incorporated by reference, may be usedto form a biodegradable body.

The filaments of the biodegradable devices may incorporate one or moredrugs that positively affect healing at the location where the stent isdelivered. In one embodiment, these drugs may include anticancer drugssuch as paclitaxel (which is commercially available as TAXOL, fromBristol-Myers Squibb in Princeton, N.J.) or docetaxel (which iscommercially available as TAXOTERE, from Phone-Poulenc Rorer inCollegeville, Pa.), fibroblast/smooth muscle cellproliferation-preventing agents, and antithrombogenic drugs such asheparin which is commercially available from Wyeth-Ayers inPhiladelphia, Pa.

One or more drugs may be incorporated into a polymer using any suitablemeans. For example, in one embodiment, the drugs as a solute may bedissolved in the biodegradable polymer as a solvent to form a solution.The solution may then be hardened into a fiber from which the stent maybe woven. In another embodiment, simple mixing or solubilizing withpolymer solutions may be utilized. The drugs may also be dispersed intothe biodegradable polymer during an extrusion or melt spinning process.In yet another embodiment, the biodegradable fibers that have alreadybeen formed may be coated with drugs.

The biodegradable filaments may be rendered radiopaque to facilitatetheir monitoring under fluoroscopy and/or their follow-up usingradiographs, fluoroscopy, or computerized tomography. The methodsdescribed above for incorporating the drugs into the polymer may be usedto mix radiopaque salts, such as tantalum, with the polymer.

As used herein, “degradation time” refers to the time during which thebiodegradable device maintains its mechanical integrity. One factor thatshould be considered in choosing a polymer in light of its degradationtime is that the polymer will loose its mechanical integrity before itis completely absorbed into the body. For example, pure polyglycolide(PGA) sutures lose about 50% of their strength after 2 weeks, and 100%at 4 weeks, and are completely absorbed in 4-6 months. For vascularapplications (i.e., applications in which the stent is placed within avessel in a body), polymers having degradation times of about one totwenty-four months may be used, depending on the application. In atypical embodiment, a polymer having a degradation time of about one tothree months may be used. In choosing a polymer for non-vascularapplications such as the esophagus, colon, biliary tree, ureter, etc.,one should consider the polymer's ability to withstand the chemicalstimuli in the given environment.

During the degradation time of a biodegradable stent, a new endotheliallayer may form on the surface of the stent. The rate of the release ofthe drugs which may be incorporated into the polymers may be controlledby the rate of degradation of the biodegradable material used. Thus, therate of release of a drug may act as a control quantity for the rate ofdegradation. At the same time, other agents such as fibronectin fromhuman plasma (commercially available from Sigma, St. Louis, Mo.) may beadded to the polymer used (using any suitable means described above forincorporating drugs into the chosen polymer) and may affect the rate ofbiodegradation. For example, fibronectin may accelerate the growth ofcells around the surrounding stent, which, in turn may accelerate theresorption reactions around the stent.

In one embodiment of a biodegradable body according to the presentinvention, one or more shape memory wires may be added to the body forreinforcement after it is formed using plain weave. Such wires maycomprise nitinol or any other comparable material above described. Inone embodiment, the wires may be formed from nitinol having about 55 to56% Nickel and 45 to 44% Titanium (Shape Memory Applications). The wireor wires may be incorporated into the woven biodegradable body bythreading the wire in and out of openings in the body several times. Inone embodiment, the manner in which the wire is threaded in and out ofopenings in the body is shown in FIG. 31. In FIG. 31, designation 520shows reinforcement wire 510 passing outside biodegradable body 500, anddesignation 530 shows reinforcement wire 510 passing insidebiodegradable body 500, thus showing how wire 510 may be threaded in andout of openings in body 500. As shown in FIG. 31, the reinforcementwire(s) 510 may be led between (i.e., parallel to) two biodegradablefilaments 540 and may follow their helical course. As shown in FIG. 31,reinforcement wire 510 may be secured to body 500 with loops 550, or anyother suitable means such as tying, twisting, or the like. Loops 550 maybe placed around a filament or around the intersection of one or morefilaments. As a result, the wire can move in harmony with the weave andwill not interfere with the movement of the filaments in the weave. Byactivating the superelasticity or thermal shape memory of reinforcementwire 510, ends 560 and 570 of body 500 may be pulled together, resultingin a tighter weave. As a result, the expansile force of the stent andits resistance to outer compression may significantly increase. In oneembodiment, loops 550 may also be used in securing body 500 to adelivery system.

In another embodiment shown in FIG. 32, in which a reinforcement wire isthreaded in and out of openings in a biodegradable body according to thepresent invention, reinforcement wire 510 may be bent at a selectedpoint located between its ends, typically at about the mid-point of thewire, and a small loop 512 may be created (similar to the small closedloops described above). As shown in FIG. 32, small loop 512 may beentwined around a filament or the intersection of one or more filaments,and reinforcement wire 510 may be threaded in and out of the openings inbody 500 as described above, and may be secured to body 500 with loops550, or any other suitable mean, as above described. Both portions 514of reinforcement wire 510 may be symmetrically led along both sides ofbody 500 following the sinuous/helical course of the biodegradablefilaments. As described earlier, by activating the superelasticity orthermal shape memory of reinforcement wire 510, ends 560 and 570 of body500 may be pulled together, resulting in a tighter weave. As a result,the expansile force of the stent and its resistance to outer compressionmay significantly increase. In one embodiment, loops 550 may also beused in securing body 500 to a delivery system.

In one embodiment, the size of reinforcement wire 510 may range fromabout 0.005 inches to about 0.012 inches. It is to be understood thatincreasing the size of reinforcement wire 510 may increase the forcewith which ends 560 and 570 are pulled together when the shape memory ofthe wire is activated. It is to be understood that using more than onewire may have the same effect as increasing the size of the wire.

In one embodiment, reinforcement wire(s) 510 may be formed around atemplate as above described. The reinforcement wire(s) may then beprogrammed with superelasticity or shape memory as described herein.

Bench-Work

With regard to the biodegradable version of the stents according to thepresent invention, the inventors have used an open-ended plain wovennylon body (that is, the filament ends were not coupled together to formclosed structures after weaving) for initial bench work. The tubularbody was woven using 0.007 inch nylon filaments. The number of filamentsused was 16, and the unconstrained diameter of the tube was 11 mm. In anunconstrained state, the size of the weave holes was approximately 1 mm.The expansile force of the tube was relatively good, and after maximumelongation the tube readily reverted to its unconstrained diameter.Compressing the tube from its two ends longitudinally, the expansileforce could be increased considerably. At the maximal longitudinalcompression, the diameter of the tubular mesh was 13 mm. Holding bothends of the tube, the stent became virtually incompressible.

A 0.006″ nitinol wire was threaded through the holes of theunconstrained mesh in the manner described earlier. The wire was astraight nitinol wire and was not formed on a template and programmedwith either shape memory or superelasticity. The straight wire causedthe mesh to elongate and the unconstrained diameter of the tubedecreased to 9.5 mm (13% lumen-loss) though the other characteristics ofthe mesh did not change. The woven tubular structure could be elongatedcompletely as well as compressed maximally.

1.5 Occluders

With reference to the illustrative embodiments shown in FIGS. 33A-G, 34,and 35, there are shown occluders for insertion and delivery into ananatomical structure. An occluder according to the present invention maybe used to substantially or completely prevent the flow of blood througha vessel. Body 700 of the occluder may be formed using plain weave bythe methods above described. The types of structures into which anoccluder according to the present invention may be placed includearteries, veins, patent ductus arteriosus, and the ureter.

In one embodiment of the present invention, an occluder may be formed byweaving a body for use as a stent as above described. The body may thenbe heated and allowed to cool as above described. The body may then beremodeled (i.e., mounted on another template in a manner similar to themanner in which the body was coupled to the first template (e.g., usinga copper support wire)), and reheated and cooled in a manner similar tothe original heating and cooling. The template that may be used in theremodeling may have the desired shape of the occluder in one embodiment.In another embodiment, a tubular template, preferably with a smallercaliber than that of the original template, may be used. In thisembodiment, after securing one end of the body to the template usingsupport wire or any other suitable means, the distance between the twoends of the body may be appropriately decreased. As a result, themid-portion of the body will balloon outward (FIG. 33B). Depending onthe distance between the two ends of the body, a series of differentshapes may be created. The shapes may include a round shape (FIG. 33A),an elongated fusiform shape (FIG. 33B), a compressed fusiform shape(FIG. 33C), a compressed fusiform shape with an inverted distal end(FIG. 33D), a flat disc configuration (FIG. 33E), a shape in which theproximal end of the occluder is inverted into the body of the occluder(FIG. 33F), a torpedo shape (FIG. 33G), etc. After achieving the desiredshape of the body, the other end of the body may also be secured to thetemplate. The body/template unit may then be heated and cooled again.The heating temperatures and times disclosed above may be utilized.

To increase the thrombogenicity of the occluder, (i.e., the ability ofthe occluder to prevent the flow of fluid) thrombogenic materials in theform of an occluding agent may be enclosed within the body. Any suitablematerial may be used for the occluding agent. The size and shape of theoccluding agent may be varied according to need. In one embodiment, oneor more threads of polyester may by used as an occluding agent. Thethreads may be coupled to the body at one or both of the ends of thebody using any suitable means such as sutures. The threads may also beplaced loosely within the body. In another embodiment, DACRON threadsmay be used as an occluding agent. The DACRON may be coupled to the bodyat one or both ends of the body using any suitable means such asmonofilament sutures, glue, or the like. The DACRON may also be placedloosely within the body.

In one embodiment of the present invention, a stretchable jacket may beconfigured to cover at least a portion of the body of an occluder (FIG.34). Any suitable material may be used for the jacket. In oneembodiment, the jacket may be made of polyurethane. In anotherembodiment, the jacket may be made of silicone. The jacket may have athickness of about 0.02 mm, but it will be understood that any suitablethickness may be substituted therefor. The jacket may be coupled toeither the inner or outer surface of the body using glue, heat, or anyother suitable means. In one embodiment, by coupling the jacket to theouter surface of the body, the body may be easily manipulated within ahollow covering such as a sheath during the insertion and delivery ofthe occluder.

The closed structures of the ends of the body used as the occluder maybe held together using any suitable means. In one embodiment, amonofilament suture (polypropylene, Prolene 5-0, 6-0, 7-0, from Ethicon)may be used to hold the closed structures of the body together bythreading the suture through the closed structures or other nearbyopenings. In another embodiment, metal clips 710 may be used to hold theclosed structures of the body together (FIG. 35). In holding the closedstructures together, in one embodiment, the closed structures may beheld together such that the tubes of the delivery system (described indetail below) may easily pass through the lumen of the occluder. Inanother embodiment, the closed structures of the ends of the body maynot be held together.

During deployment of such as occluder, the interventionalist is alwaysable to correct any misplacement by simply restretching the wire meshand repositioning the body using the delivery system. Even after thedistal end of the occluder has been released, the proximal end stillremains attached to the delivery system offering another safety featurefor removal of the occluder.

The single wire embodiment may also be utilized as a structure forcausing vessel occlusion. Such an occluder should have at least twoloops. FIGS. 57A-D illustrate various single wire embodiment occluders.FIG. 57A illustrates body 700 on template 300 after having been formedthereon using, for example, either the hand weave or machine weavemethod described above. As shown, body 700 of the occluder has 3 loops.At this stage of the development of the occluder illustrated in FIG.57A, body 700 is simply a single wire embodiment stent.

After the body/template unit has been annealed using, for example, theannealing method described above for imparting body 700 withsuperelastic properties, body 700 may be removed from template 300. Body700 may then be stretched by pulling the two ends thereof longitudinallyapart, and collars 702 may be slipped over either end and placed at thelocations where first segment 704 and second segment 706 cross eachother. Collars 702 may be small pieces of metal, such as small pieces ofa nitinol tube (commercially available from Shape Memory Applications,Santa Clara, Calif.). In doing this, segments 704 and 706 extend betweenthe loop-defining locations hidden by collars 702 so as to form loops710. A collar 702 may also be placed around the ends of the wire formingbody 700. At the loop-defining locations, which are hidden by collars702, segments 704 and 706 may be positioned adjacent to each other. Asused herein, segments that are “adjacent” to each other may or may nottouch each other, but such segments are positioned in close proximity toeach other such that the distance separating them is generally no morethan about 1 mm. The length of the wire segments covered by collars 702should be sufficiently short so as not to impede the flexibility of thesingle wire embodiment occluder.

Although not shown, it will be understood to those of skill in the art,with the benefit of this disclosure, that any suitable means may be usedto secure segments 704 and 706 adjacent to each other in theloop-defining locations. Such means include wrapping the segmentstogether with any suitable wire, crimping a piece of metal around thesegments, welding the segments together, and the like.

With collars 702 in place, the shapes of loops 710 are altered such thatloops 710 possess generally compressed shapes. As shown in FIG. 57B, thetwo largest of the three loops 710 have fairly pronounced compressedshapes relative to the smallest loop 710. The compressed shape mayexaggerated (i.e., made more compressed) by decreasing the distancebetween collars. Laterally pulling the portions of segments forming agiven loop apart may be done to alter the distance between collars. Thecollars should maintain the shapes of the loops and thereby stabilizethe occluder within the anatomical structure into which it is delivered.However, the collars may be crimped to further improve their ability tomaintain the shapes of the loops. In this same regard, body 700 may besecured to a template having a suitable shape and re-annealed so thatthe compressed shapes of loops 710 are maintained. Further, re-annealingbody 700 may improve the expansile force and resulting self-anchoringcapability of the single wire embodiment occluder.

The number of loops utilized to form a single wire embodiment occludermay be reasonably increased. For example, an occluder formed using thesingle wire embodiment may have 3, 4, 5, 6 or more loops.

The shape of the loops of the single wire embodiment occluders may bevaried as desired to best cover the cross-section of the anatomicalstructure to be occluded in a manner that will likely cause occlusion inthe most rapid manner possible. Accordingly, a single wire embodimentoccluder may have loops that possess differing sizes, such as anoccluder having one or more loops near one end that are smaller than oneor more loops near the other end of the occluder. As used herein, thetotal length of the segments that define a loop that is “smaller” thananother loop of a single wire embodiment is less than the total lengthof the segments that define the larger loop. In another embodiment, theoccluder may appear tapered, where the loops decrease in size from oneend to the other. In another alternative embodiment, one or two smallloops may be arranged at or near the mid-portion of a single wireembodiment occluder, while the loops at the proximal and distal ends maybe larger by comparison and possibly equal to each other in terms ofsize.

In order to increase the thrombogenicity of the single wire embodimentoccluders, various occluding agents may be attached to the occluder. Anysuitable material may be used for the occluding agent. For example,pieces of a metal coil, such as one made from stainless steel, may bepulled over the wire segments prior to slipping collars over them. Inthis regard, the single wire embodiment occluder may be re-annealed asdescribed above, the collars may be removed, the coil pieces may beplaced over the segments, and the collars may be replaced at theloop-defining locations. As illustrated in FIG. 57C, coil pieces 714 areplaced over the segments between collars 702. The coil pieces may alsobe wires, such as stainless steel or nitinol wires, that are manuallywrapped around the segments and attached to the segments in any suitablefashion. The coil pieces may be pre-formed hollow pieces of coil madefrom any suitable metal or alloy.

Thrombogenic filaments (such as polyester fibers) may also be attachedto coil pieces 714 to further increase the thrombogenicity of the singlewire embodiment occluders. As illustrated in FIG. 57D, polyester fibers716 are attached to coil pieces 714 at various locations along the coilpieces. The length of the thrombogenic filaments may vary, as may thedistance between the filaments, in order to ensure that the resultingthrombogenicity of the single wire embodiment occluder is best-suited tothe application. The thrombogenic filaments may be individual fibers orbundles of fibers.

In another embodiment, segments of the single wire embodiment occludermay be covered by bundles of thrombogenic filaments, such as filamentsmade of polyester, such that the bundles resemble the coil pieces, andadditional thrombogenic filaments, such as polyester fibers, may beattached to or braided with the bundles of filaments such that theyextend away from the covered segments in the same fashion as fibers 716illustrated in FIG. 57D.

Delivery Systems for Stents, Stent Grafts and Occluders

With reference to FIG. 3, the delivery system 20 for body 10, taperedbody 100 and body 700 (including biodegradable versions thereof), mayconsist of two flexible tubes arranged coaxially. These tubes may beformed of material such as TEFLON or NYLON, which are commerciallyavailable from Cook, Inc. (Bloomington, Ind.), or other similarlysuitable materials. It is to be understood that material that is lessflexible or firmer than TEFLON may also be used. Further, it is to beunderstood that material with a thinner wall thickness than that ofTEFLON tubing, such as the material from which the WALLSTENT deliverysystem is formed, may be utilized. In one embodiment, one or both tubesmay be made of metal, such as nitinol, which is commercially availablefrom Shape Memory Applications. Nitinol tubes may be particularlywell-suited for use in delivery systems that are relatively large orrigid, such as for tracheal or bronchial stenting.

The size of the outer diameter of the distal, small caliber tube 22 mayrange from 2.5 to 7.5 French (“F”) depending on the application of thestent, the size of the stent, and the number of securing wires (to bediscussed below) that may be used to secure the stent to tube 22 (to bediscussed below). For coronary applications, for example, the size oftube 22 may be about 3-F. For delivery of a medium stent into the renalor carotid arteries, for example, the size of tube 22 may be about 5-F.The length of tube 22 may range from 80 cm to about 120 cm depending onthe application of the stent and the size of the stent. In an exemplaryembodiment, for example, for delivery of an iliac artery stent from acontralateral approach, the length of the tubing may be about 90 cm. Inanother exemplary embodiment, for carotid artery stenting, the length ofthe tubing may be about 110 cm. The size of the stent may also haveaffect the length of tube 22. Thus, in an exemplary embodiment, thelarger the stent diameter, the longer the stent is in its completelyelongated state.

Tube 22 as well as tube 40 (discussed below) may be provided with aflange or hub near its proximal end so as to allow for control of theposition of tube 22 during delivery of the stent. In an exemplaryembodiment as shown in FIG. 25, a push button lock/release mechanism 200(such as a FloSwitch® HP device from Meditech/Boston Scientific Corp.,Watertown, Mass. or a CRICKETT device from Microvena in White Bear Lake,Minn.) may be utilized for securing tube 40 to tube 22 when necessary.As further illustrated in FIG. 25, an end fitting 204 with a side armmay be utilized with a Luer-lock mechanism and/or tightening screws forfurther facilitating delivery of the stent. Although not shown, it willbe understood by those of skill in the art, with the benefit of thisdisclosure, that the hub or flange that may be provided on the end oftube 22 may be used to facilitate the connection between end fitting 204and tube 22. Similarly, although not shown, it will be understood bythose of skill in the art, with the benefit of this disclosure, that theend of tube 40 may be provided with a hub or flange that may be used tofacilitate the connection between push button lock/release mechanism 200and tube 40. End fitting 204 may be equipped with separated lumens in adouble channel system. One or more steerable guidewires 203 may beutilized in the lumen of tube 22 and in the lumen of end fitting 204 forfacilitating delivery of the devices described herein.

It is to be understood that radiopaque markers may be placed on tube 22at appropriate locations in a manner known in the art in order to betterenable viewing of tube 22 using fluoroscopy during delivery of thestent.

As shown in FIG. 3, the distal, smaller caliber tube 22 is equipped withproximal hole 24 and distal hole 26. Distal hole 26 may be typicallylocated between about 0.5 and about 3.0 cm from distal end 28 of tube22, most typically about 1 cm. The location of the radiopaque markers ontube 22 may affect this distance. The distance between holes 24 and 26may be typically about 3 to 8 mm, but most typically about 3 to 5 mm.This distance may be affected by the size of the securing wire 30. Forexample, the distance between the holes may decrease as the diameter ofwire 30 decreases.

Securing wire 30 may be placed within the lumen of tube 22 (the dottedline indicates that securing wire 30 is located within tube 22), and maypass through holes 24 and 26 so as to form a small-profile, tightsecuring loop 32 between the two holes. Distal end 34 of securing wire30 terminates at or near distal end 28 of tube 22. Proximal end ofsecuring wire 30 may be connected to a handle 206 as shown in FIG. 25.

Securing loop 32 holds the small loops (6 and 106) or bends (8 and 108)of distal end (12 or 102) of body 10 or tapered body 100 in positionduring delivery (delivery being described in more detail below.)Advantageously, securing loop 32 also prevents premature delivery of thestent. Thus, prior to delivery of the stent, distal end 34 of securingwire 30 passes out through proximal hole 24, passes through the smallloops or bends of the stent, and passes back into the lumen of tube 22through distal hole 26, terminating prior to distal end 28, thussecuring the distal end of the stent to tube 22. It is to be understoodthat securing wire 30 may pass through one of the openings in the plainweave of body 10 or tapered body 100 other than the small loop (6 and106) or bend (8 and 108).

In most applications, securing wire 30 ranges in size from about 0.006inches to about 0.011 inches in diameter. However, the size of securingwire 30 in any given application depends upon several factors. Forexample, a larger (in terms of diameter) securing wire provides moreresistance to the propensity of a stretched stent to contract than doesa smaller wire. Additionally, when more than one securing wire isutilized, the size of the wires can be less than if only one securingwire were used. The securing wires of the present invention may be madeof any of the shape memory materials described above. In one embodiment,the securing wires of the present invention are made of nitinol. Inanother embodiment, the securing wires of the present invention may beformed of nitinol having about 55 to 56% Nickel and about 45 to 44%Titanium (commercially available from Shape Memory Applications). In anembodiment in which the securing wires of the present invention arenitinol (including wires 30 and 46, discussed below), the nitinolsecuring wires may be heat treated as described herein or purchased froma manufacturer such that the superelastic properties of the nitinol maybe utilized.

The proximal, larger caliber tube 40 is also equipped with proximal anddistal holes 42 and 44 typically located in approximately the samelocation from distal end 41 of tube 40 as are holes 24 and 26 fromdistal end 28 of tube 22. The distance between holes 42 and 44 is alsocomparable to the distance between the holes in tube 22.

The size of the outer diameter of the proximal tube 40 may range fromabout 4.5-F to about 10-F depending on the application of the stent, thesize of the stent, and the number of securing wires that may be used tosecure the proximal end of the stent to tube 40 (to be discussed below).For coronary applications, for example, the size of tube 40 may be about5-F. In an exemplary embodiment, for carotid artery stenting, the sizeof tube 40 may be about 7 to about 8-F. The length of tube 40 may rangefrom about 70 cm to about 110 cm depending on the application of thestent and the size of the stent. In an exemplary embodiment, the lengthof tube 40 may typically be about 10 cm to about 20 cm shorter than thelength of tube 22. It is to be understood that the proximal end of tube22 may extend beyond the proximal end of tube 40, just as distal end 28of tube 22 extends beyond distal end 41 of tube 40 as shown in FIG. 3.In an exemplary embodiment, the factor that may primarily influence thelength of the delivery system (i.e., tubes 22 and 40) is the distance ofthe stented region from the access site (typically the femoral artery).As with tube 22, tube 40 may be provided with a flange or hub near itsproximal end so as to allow for control of the position of tube 40during delivery of the stent.

It is to be understood that radiopaque markers may be placed on tube 40at appropriate locations in a manner known in the art in order to betterenable viewing of tube 40 using fluoroscopy during delivery of thestent.

Securing wire 46 is positioned with the lumen of tube 40, and formssmall-profile, tight securing loop 48 in the manner above described.Securing loop 48 holds closed structures (4 and 104) of proximal end (2and 112) of body 10 and tapered body 100 in position during delivery,and advantageously prevents premature delivery of the stent. It is to beunderstood that securing wire 46 may pass through one of the openings ofthe plain weave of body 10 or tapered body 100 other than the closedstructures. The closed structures are secured using the manner describedabove for the loops or bends.

Securing wire 46 and securing wire 30 may be formed from the samematerials as the wires making up the stent. Additionally, securing wire46 may be approximately the same size as securing wire 30, and the sametypes of factors discussed above should be considered in sizing securingwire 46.

In FIG. 3, although only one securing loop is shown on either tube, itis to be understood that more than one securing loop may be utilized oneach tube to secure the proximal and distal ends of the stent. Moresecuring loops may be achieved with the same securing wire, or by usingmore securing wires. As discussed above, the number of securing wiresthat may be used may depend on several factors, such as the amount offorce needed to elongate or constrain the stent prior to delivery. Forexample, the more resistant the stent is to elongation, the moresecuring wires may be used in order to facilitate the stretching orelongation of the stent on the delivery system. By this means, the endsof the stent can be suspended evenly around the tubes and the frictionbetween tubes and the profile of the elongated stent can be reasonablydecreased. An additional factor affecting the number of securing wiresmay be the use of a guidewire (described below). In an exemplaryembodiment of the delivery system according to the present invention, aguidewire may be utilized during delivery (described below). As aresult, the use of a guidewire will affect the amount of space withintube 22 available for the use of the securing wire or wires. It is alsoto be understood that securing wires having tapered distal ends may beused no matter how many securing wires are used.

Body 700 may be secured to the delivery systems of the present inventionthe delivery system depicted in FIG. 3, in the same manner in which body10 and tapered body 100 may be secured to these delivery systems asabove described. In one embodiment in which the ends of body 700 aresecured to tubes 22 and 40, one small-profile, tight securing loop maybe used to secure each end.

With reference to another illustrative embodiment of the delivery systemaccording to the present invention shown in FIG. 4, delivery system 50has tube 22 equipped with proximal and distal holes 24 and 26 in themanner above described. As shown, delivery system 50 may consist ofthin-walled sheath 52 arranged coaxially with tube 22. Sheath 52 may beformed of materials comparable to those from which tubes 22 and 40 areformed. Sheath 52 may be about 1 cm to about 2.5 cm in length, buttypically about 1.5 cm. The distal end 54 of sheath 52 is connected orattached to tube 22 by gluing, melting, heating or any other suitablemeans at a location typically between about 8 cm to about 20 cm fromdistal end 28 of tube 22, but most typically about 15 cm.

As shown in FIG. 4, delivery system 50 may consist of inverse tabs 60which are connected to or engaged with the distal end of tube 40.Inverse tabs 60 are connected to or engaged with tube 40 by any suitablemeans, including the use of a metal ring friction fitted around tube 40,to which tabs 60 may be soldered, welded, or integrally formed. Inversetabs 60 are connected or engaged with tube 40 at a location that may bedetermined based on the completely stretched length of the stent.Inverse tabs 60 may be made of any suitable material, including thosefrom which the wires of the stent may be made, and further includingstainless steel and other similar materials.

The following description applies to both body 10 and tapered body 100.However, reference is made only to body 10 by way of example. Inversetabs 60 secure proximal end 2 of body 10 in the following generalmanner. Inverse tabs 60 are placed within the lumen of body 10. Proximalends 62 of inverse tabs 60 are then “threaded” through closed structures4 or other holes located near the proximal end 2 of body 10. Tube 40 isthen moved in a proximal direction until closed structures 4 (or otherholes) are secured by the inverse tabs. The space created between sheath52 and tube 22 may be used to house inverse tabs 60 as below described.

Delivery of the Stents, Stent Grafts and Occluders

Body 10 and tapered body 100 (including biodegradable versions thereof),and body 700 may be delivered in a similar manner. Thus, the followingdescription of methods of delivery for the stents and occludersreferences only body 10 by way of example.

Prior to delivery, a stent in the form of body 10 may be manuallysecured to tubes 22 and 40. This may be accomplished by using eithersecuring loops in the manner described above with reference to FIG. 3(hereinafter “version 1”), or by securing loop 32 and inverse tabs 60 inthe manner described above with reference to FIG. 4 (hereinafter“version 2”).

In either version, a stent is first stretched so as to reduce itsdiameter by an amount appropriate to allow delivery to occur. Thus, thestent may be stretched maximally or just to an extent such that it maybe inserted into a vessel or non-vascular structure, and may passthrough the lumen of the vessel or non-vascular structure as the stentis being positioned prior to being delivered into the vessel ornon-vascular tubular structure. When delivering the single wireembodiment discussed above, it should be noted that the ratio of theconstrained length of the body to the unconstrained length of the bodymay be significantly greater in this embodiment than in the embodimentsthat utilize multiple wires. Therefore, the single wire embodiment mayrequire a greater length within the vessel or non-vascular structure inwhich to be manipulated and prepared for delivery than may otherembodiments that utilize multiple wires.

The stent to be delivered may be stretched by increasing the distancebetween the distal ends of tubes 22 and 40. This may be accomplished bymoving or sliding tube 40 in a proximal direction over tube 22 whileholding tube 22 stationary, or by moving or sliding tube 22 in a distaldirection while holding tube 40 stationary, or by moving or sliding thetubes in the aforementioned directions simultaneously. Once the stenthas been appropriately stretched, tubes 22 and 40 may be locked togetherin a manner well known in the art, such as with the use of tighteningscrews or push button mechanisms which are easily lockable andunlockable. If version 2 is used, an outer sheath 70 as shown in FIG. 5Amay be used to cover inverse tabs 60.

In an illustrative embodiment, it is preferable to use a guidewireplaced through the lumen of tube 22 for use in guiding the stent to itsproper location in a manner well known in the art. The guidewire may beformed of any material from which the wires forming the stent may bemade. The guidewire may be between about 0.014 inches and about 0.035inches in diameter. In one embodiment, the guidewire may be made ofnitinol (commercially available from Microvena). In another illustrativeembodiment, a hollow covering such as a sheath may be placed over astent secured to tubes 22 and 40 so as to prevent contact between thestent and the vessel or non-vascular structure during delivery of thestent.

The first step of inserting either delivery system into the body is toestablish an access (arterial or venous). After puncturing the vesselusing an adequate needle, a guidewire is inserted into the body. Theneedle is removed, and over the guidewire an introducer sheath with acheck-flow adapter and preferably with a side-port is advanced. Theguidewire is then removed. This introducer sheath, the size of which isdetermined by the size of the delivery system to be used, serves as anaccess for the intervention.

In version 1, when the stent, still stretched on delivery system 20, ispositioned in the desired location of the vessel or non-vascular tubularstructure to be stented, the sheath covering the stent may be withdrawn,and the tubes may be unlocked. The stent may be positioned and thenshortened so as to achieve its unconstrained diameter in a variety ofmanners. In an exemplary embodiment, the distal end of the stent may bepositioned in its final location prior to shortening the stent. Then,while maintaining the position of the distal end of the stent, tube 40,to which the proximal end of the stent is secured, may be moved distallyover tube 22. As a result, the distance between the two ends of thestent will be shortened and the diameter of the stent will approach, andmay reach, its unconstrained, preformed diameter. In another embodiment,the proximal end of the stent may be positioned in its final locationprior to shortening the stent. As such, tube 40 may be held steady andtube 22 may be moved proximally within tube 40 in order to shorten thestent. In another embodiment, the middle of the stent may be positionedin its final location prior to shortening, and tubes 22 and 40 may bemoved toward each other by equivalent distances. The many manners inwhich the stent may be positioned and subsequently shortened duringdelivery thereof benefit the operator by providing him or her with theversatility necessary to deliver stents within a variety of anatomicalstructures.

The ability to compress the woven devices disclosed herein with thepresent delivery systems prior to releasing them is advantageous forseveral reasons. Not only does it assist the operator in achievingadequate contact between the woven device and the wall of the anatomicalstructure such that the woven device is anchored as securely aspossible, it also allows the compressed device to occupy the leastamount of space along the length of the anatomical structure aspossible. When using the present occluders, for example, care should betaken to limit the space along the length of the structure whereocclusion is taking place so as to avoid potential complications likethe undesired occlusion of side branches, and the prevention of theformation of collateral vessels supplying the structures not affected bythe treated lesion. Further, when using the present filters, forexample, the space along the vessel available for filter placement maybe limited by the presence of the thrombotic disease and/or otheranatomical considerations, such as the proximity of renal veins in theIVC, the short, free segment of the SVC, etc.

Another advantage afforded by the present delivery system relating tothe ability of an operator to manipulate either or both ends of thewoven body being delivered prior to releasing those ends is the abilityafforded the operator to position the present woven devices accuratelyin irregularly diseased anatomical structures. Anatomical structures arefrequently irregularly stenosed; the distensibility or enlargeability ofthe diseased segment may be irregular due to the presence of tough scartissue or a tumor, for example; and lengthy vessels are naturallytapered. Because both ends of one of the present woven devices may besimultaneously manipulated while using the middle of the woven device asa point of reference prior to release, the operator may be able toposition the mid-portion of the device (such as a stent) proximate themid-portion of the diseased segment of the vessel and maintain thatrelationship while simultaneously withdrawing tube 22 and advancing tube40 so as to accurately position the stent along the diseased segment.Further, by increasing the ability of the operator to accuratelyposition the woven device and, correspondingly, reducing the possibilitythat the woven device will need to be resheathed and reinserted, thepresent delivery systems allow the operator's job of delivery lesspotentially disruptive to the diseased segment of the patient.

Additionally, another advantage flowing from the fact that the presentdelivery systems allow for compression of woven devices lies in theresulting ability of the operator delivering a stent graft having arelatively non-stretchable graft material like PTFE to achieve a meshtightness that, in turn, may serve to create better contact between boththe woven stent and the graft material as well as between the stentgraft and the wall of the anatomical structure.

One of the benefits of using the present stents with the presentdelivery systems is that the anatomical structure being treated canalways be overstented. The diameter of an anatomical structure that is“overstented” is slightly smaller than the unconstrained diameter of thestent delivered therein. In contrast, overstenting is not necessarilyachievable using delivery systems that do not possess the presentdelivery systems' capability to manipulate the distance between the endsof the device being delivered prior to stent release. Stents that arereleased using such delivery systems may remain elongated within theanatomical structure into which they are delivered and, as a result, maynot have a radial force sufficient to resist outer compression, which inturn could compromise the patency of the structure. Further,insufficient radial force could lead to stent migration. With thepresent delivery system, however, the present stents, for example, maybe chosen such that their diameter is significantly greater than onehundred and ten percent of the anatomical structure being stented (110%being the norm for balloon-expandable stents, for example), such as onehundred and twenty percent, for example. Consequently, the presentstents may be delivered so as to be slightly elongated within theanatomical structure in which they may be delivered (i.e., the meshtightness of the stent may be less than the tightest achievable), yetmay retain enough expansile force to keep the structure patent,withstand outer compressive forces and be unlikely to migrate.

The overdistention or overstenting of an anatomical structure using oneof the present stents that is substantially or completely compressed maybe beneficial for several reasons. For example, the overstenting helpsensure that the stent will remain fixed in its original location andwill not likely migrate. The inventors have discovered that when thepresent woven bodies are compressed prior to being released, theycontact the anatomical structure more securely than if they are releasedwithout first being compressed. Further, as the overstenting may beachieved using a substantially or maximally compressed stent, thenear-maximum or maximum radial force of the stent may also increase thestent's ability to withstand greater outer compressive forces withoutelongating and thereby compromising the patency of the structure beingstented. Although overstenting is described above, those of skill in theart will understand with the benefit of the present disclosure that thesame principle applies with equal force to the woven filters andoccluders disclosed herein, and the single wire embodiments of each, andmay be achieved in the same manner.

The Wallsten patent discloses a delivery system for the WALLSTENT thatallows the distance between the ends thereof to be manipulated prior tothe release of the WALLSTENT. However, this delivery system (depicted inFIGS. 5 and 6 of the Wallsten patent) suffers from a number ofshortcomings that are overcome by the present delivery systems. Forexample, the Wallsten delivery system involves a number of intricateparts (such as annular members, latches, rings, cables for displacingthe rings, and a casing) that version 1 does not utilize and that wouldlikely be time-consuming and expensive to manufacture and assemble. Incontrast, the simple design of version 1—i.e., two tubes and multiplesecuring wires—has few parts, and those parts are easily obtainable.

Another advantage afforded by the present delivery systems is that thedevice being delivered is clearly visible during delivery. No parts,once any delivery sheath has been removed from around the presentdelivery systems, obstruct the view of the location of the ends of thedevice being manipulated. Additionally, the profile of the presentdelivery systems is no greater than that of the device being deliveredover tube 40 (the larger of the delivery tubes). This is advantageousbecause the smaller the profile of the delivery system, the less likelythe diseased segment of the structure will be unnecessarily disrupted ortraumatized during the positioning and delivery of the woven device.

It is possible to overstent anatomical structures utilizing the presentdelivery systems and present stents through the longitudinal movement oftubes 40 and 22 in both version 1 and version 2, the latter of which isdescribed below. As described above, these tubes may be moved relativeto each other such that the stent being delivered is compressedmaximally or nearly maximally prior to being released.

If the stent is not in the desired location after reaching its preformeddiameter, it can advantageously be restretched and repositioned bymoving tube 40, proximally and locking tube 40 to tube 22 if so desired.After locking has occurred, the stent may be repositioned and theprocess above described may be repeated as needed. This process may becomplete when the stent is positioned in the desired location, and thestent fits in the vessel or non-vascular tubular structure in a way thatthe stent is nearly maximally expanded and/or the tissue of the vesselor non-vascular tubular structure is stretched slightly.

After performing this process, the distal end of the stent may then bereleased from its secured position. The distal end of the stent may beso released by pulling securing wire 30 (or wires) back into the lumenof tube 22. If the stent is still in the proper position, the proximalend of the stent may be released in the same manner so as to deliver thestent into the vessel or non-vascular structure, and the delivery systemmay be withdrawn back into a sheath and out of the body. If the stent isno longer positioned in the desired location after releasing the distalend of the stent, the stent may be pulled proximally back into a sheathby proximally moving tube 40 to which the proximal end of stent is stillsecured and/or distally moving the sheath. After doing so, the stent anddelivery system may be removed from the body.

It is to be understood that the proximal end of the stent may bereleased from its secured position prior to releasing the distal end ofthe stent. Upon doing so, however, the ability to withdraw the stentback into a sheath (if a sheath is used) as described above is no longerpresent. Therefore, typically, the proximal end may be released firstwhen the desired location of the stent will likely be maintained aftersuch release.

In version 2, the stretched stent may be positioned in the desiredlocation of the vessel or non-vascular tubular structure to be stented.Then, prior to unlocking the tubes, a sheath used to cover the stent, ifused, may be proximally withdrawn so as to expose the stretched stent.Also prior to unlocking the tubes, outer sheath 70 covering inverse tabs60 may be moved proximally so that inverse tabs 60 are exposed (see FIG.5A). In an exemplary embodiment, the outer sheath 70 may be withdrawnbut not removed. The tubes may then be unlocked. It is to be understoodthat the tubes may be unlocked prior to withdrawing either a sheath usedto cover the stretched stent, or outer sheath 70. Once this hasoccurred, either the distal end or proximal end of the stent may bereleased from its secured position as follows. In an exemplaryembodiment, it may be preferable to release the distal end of the stentfirst because the secured proximal end may offer the possibility ofremoving a misplaced stent as above described. It is to be understood,however, that because of the completely controlled nature of thedelivery system of the present invention, the need to remove a misplacedstent may be very low, and, therefore, the proximal end of the stent maybe released first without great risk.

When the distal end is to be released first, tube 40 may be moveddistally over tube 22 (see FIGS. 5B and C) until the distal end of tube40 reaches a pre-determined point located on tube 22, which in anexemplary embodiment, may be denoted through the use of a radiopaquemarker. The point is located along tube 22 such that the proximal end ofthe stent will not be unhooked from inverse tabs 60 when the distal endof tube 40 reaches it. When the point is reached by the distal end oftube 40, the tubes are locked together. Additionally, another marker mayalso be used on the proximal shaft of tube 22 to denote the same point.If the stent is no longer in its ideal position at this point, outersheath 70 may be moved distally and/or tube 40 may be moved proximallyto cover inverse tabs 60, and the delivery system and the stent may bewithdrawn into a sheath and removed from the body. If the properposition has been achieved, the distal end of the stent may then bereleased in the manner above described. Next, the proximal end of thestent may be released by unlocking the tubes, and moving tube 40distally over tube 22 until inverse tabs 60 release the openings orclosed structures through which they were threaded. Tube 40 may then befurther advanced distally until inverse tabs 60 are hidden or housedwithin sheath 52 as shown in FIG. 5D. At this point, the tubes may belocked together to maintain the position of the inverse tabs withinsheath 52. After both ends of the stent have been released (see FIG.5E), delivery system 50 may be withdrawn into a sheath and removed fromthe body.

In version 2, if the proximal end of the stent is to be released first,the sequence of events just described may occur (including the abilityof the stent to be restretched and repositioned), except that the distalend of tube 40 may extend distally beyond the predetermined point suchthat inverse tabs 60 unhook the proximal end of the stent and then go onto being hidden or housed within sheath 52 as shown in d. of FIG. 5.After the proximal end has been released, the distal end of the stentmay be released in the manner above described. At this point, the tubesmay be locked together to maintain the position of the inverse tabswithin sheath 52. Delivery system 50 may then be withdrawn from the bodyas above described.

The delivery of the present stent grafts that utilize graft materialthat is stretchable as described above may be achieved with the samedelivery systems and in the same manner as the delivery of the present“naked” stents. When a graft material that is formed from relativelynon-stretchable material, such as PTFE, is utilized, however, althoughthe same delivery systems may be utilized, the manner in which the stentgraft may be delivered is slightly different from the manner in whichthe naked stents may be delivered in terms of the manner in which thestent graft may be repositioned, if necessary.

For example, if after releasing the distal end of the stent graft,whether the graft material is attached to the stent at the proximal ordistal end thereof, the stent may be restretched over the delivery tubesand the stent's completely elongated position may be secured using theproximal lock mechanism. Then, the introducer sheath may be advancedover the proximal end of the stent graft, possibly as it is rotated, inorder to recapture the graft material and the stent itself. Attachingthe graft material to the stent at the proximal end thereof may make iteasier to re-sheath the graft material using the process just described,and thus may facilitate repositioning, if necessary, because the graftmaterial may take on a funnel shape prior to the release of the proximalend of the stent graft.

Delivery of Stents in Side-By-Side Relationship

The delivery of these stents may be accomplished relativelysimultaneously, such that neither stent occupies more space within theaorta than does the other. Initially, the stents may be secured toeither version of the delivery systems described above using the methodsdescribed above. As illustrated in FIGS. 58A-D, in addition to securingthe ends of the stent to tubes 22 and 40, the stent may also be securedto either tube (tube 22 as shown, for example) near the portion of thestent that will be positioned near the bilateral aorto-renal junction830, which consists of aorta 832, left renal artery 834 and right renalartery 836. FIGS. 58A-D illustrate only one stent being delivered, butit will be understood to those of skill in the art, with the benefit ofthis disclosure, that, as stated above, two stents may be released anddelivered relatively simultaneously in the fashion described below. Asshown, guidewire 203 may be utilized to enhance the maneuverability ofthe delivery system. (The fittings that may be used to secure tubes 22and 40 to each, which are illustrated in FIGS. 25 and 26, are notillustrated in FIGS. 58A-D for the sake of simplicity.) This thirdsecured portion may be achieved using the low-profile, tight securingloops described above. After stretching the stent on the delivery systemand positioning the distal end of the stent in right renal artery 836 inthe manner described above (FIG. 58A), the release and delivery of thestent may take place by first releasing the proximal end of the stent(FIG. 58B), then the distal end (FIG. 58C), and finally the portion ofthe stent near junction 830 (FIG. 58D). Tubes 22 and 40 and guidewire203 may then be withdrawn from the patient. It will be understood tothose of skill in the art, with the benefit of this disclosure, that therelease of the various secured portions of the stents may take place inany order suited to the anatomical structure in question.

Combined Treatment of Aneurysms Consisting of Stent Placement andTranscatheter Embolization

In one embodiment of the present invention, the straight stent may beused for aneurysm treatment without being equipped with a graftmaterial. In this embodiment, the “naked” stent may serve as a scaffoldfor developing an endothelial layer on the newly formed vessel lumen,while the aneurysmal sac may be excluded from circulation bytranscatheter embolization.

Generally, the stent may be delivered into place, and an embolic agent96 may be inserted into the surrounding aneurysmal sac as shown in FIG.36.

As shown in FIG. 36, once the stent is in the appropriate position, anangiographic catheter 95 (5-French to 7-French) that is chemicallycompatible with the embolic agent (and not made from polyurethane whenthe embolic agent contains DMSO) may be inserted and advanced into thelumen of the stent. In advancing the angiographic catheter into thelumen of the stent, one may use the same guidewire which may have beenused in delivering the stent. However, one may advance the angiographiccatheter without the use of a guidewire. An adequately sizedmicrocatheter 97 (2-French to 4-French) that is also chemicallycompatible with the embolic agent may then be advanced through theangiographic catheter, on an appropriate size guidewire (0.014-inches to0.025-inches). The tip of the microcatheter may then be led through theweave of the stent into the aneurysmal sac. If the openings in the weaveof the stent are approximately 2.0 to 2.5 mm, angiographic catheter 95may also be advanced into the aneurysmal sac. An embolic agent 96 maythen be inserted into the aneurysmal sac through the microcatheter.Embolic agent 96 may be chosen so as to be: non-toxic,non-irritant/reactive to the tissues; easily handled; suitable forcontinuous injection; adequately radiopaque; capable of filling thespace contiguously without leaving unoccupied spaces; andnon-fragmented, thereby not getting back through the stent's weave intothe newly formed lumen which could result in peripheral embolization.

Although, several fluid embolic materials (alcohol, poly-vinyl alcohol,cyanoacrylates, Ethibloc etc.,) are available for transcatheter vesselocclusion, none of them is considered ideal or even suitable for thispurpose. Recently, a nonadhesive, liquid embolic agent, ethylene vinylalcohol copolymer (EVAL), has been used clinically for treatment ofcerebral AVMs in Japan (Taki, AJNR 1990; Terada, J Neurosurg 1991). Theco-polymer was used with metrizamide to make the mixture radiopaque andmay serve as the embolic agent for the present invention.

Very recently, a new embolic agent (similar to EVAL), EMBOLYX E(ethylene vinyl alcohol copolymer) (MicroTherapeutics Inc., SanClemente, Calif.) was developed which was designed for aneurysmtreatment (Murayama, Neurosurgery 1998), and may be utilized as anembolic agent in one embodiment of the present invention. The embolicagent is composed of a random mixture of two subunits, ethylene(hydrophobic) and vinyl alcohol (hydrophilic). Micronized tantalumpowder is added to it to obtain an appropriate radiopacity, and DMSO(di-methyl sulfoxide) is used as an organic solvent. When the polymercontacts aqueous media, such as blood, the solvent should rapidlydiffuse away from the mixture causing in situ precipitation andsolidification of the polymer, with formation of a spongy embolus andwithout adhesion to the vascular wall. Any kind of material withcharacteristics similar to those of EMBOLYX E may be used as an embolicagent for the present invention.

The method just described may be utilized when the stent is covered aswell. In such an embodiment, angiographic catheter 95, which may be 5-Fin size, and microcatheter 97, which may be 3-F in size, may advancedinto the lumen of the covered stent as described above. A trocar, suchas one having a 0.018-inch pencil-point or diamond-shaped tip and madeof any suitable material such as stainless steel or nitinol, may then beinserted into the lumen of microcatheter 97. The sharp tip of the trocarmay extend beyond the tip of microcatheter 97 by about 2 to 4 mm. Theproximal ends of microcatheter 97 and the trocar may be locked togetherusing a Luer lock mechanism. By doing so, a sheath-needle unit (wellknown in the art) may be created, which may then be used to puncture thegraft material and the stent mesh. Thereafter, using fluoroscopy and/orCT in guiding the sheath-needle unit, the sheath-needle unit may besafely advanced into the aneurysmal sac. The trocar may then be removed,and microcatheter 97 may be used for injecting the embolic agent asdescribed earlier.

Both abdominal and thoracic abdominal aneurysms may be treated as abovedescribed. In some other locations (e.g., external iliac artery),pesudoaneurysm and/or tumor-induced corrosive hemorrhage may also betreated as above described.

The size of the delivery system that may be used to deliver a stentwithout a graft cover may be sufficiently small, such that insertion ofthe stent into the vessel may take place following a percutaneousinsertion. The delivery system would also be well-suited to negotiatingthrough tortuous vascular anatomy. The treatment described above may beperformed using interventional radiology techniques, thereby eliminatingthe need for surgery. The embolization may occlude the lumbar arteriesfrom which the excluded aneurysmal sac is frequently refilled. As aresult of using the treatment described above, the endoleak from thepatent lumbar arteries may be eliminated.

2. Filters Low-Profile Woven Cava Filters

The wires of the cava filters of the present invention may be made ofthe same materials as the wires of the stents. The same number of wiresmay be used in forming the cava filters as are used to form the stents.However, in an exemplary embodiment, less wires are preferably used forthe cava filters than for the stents. As with the stents, in anexemplary embodiment, as few as 5 wires may be used to form the cavafilters for any given application except the single wire embodiment,which utilizes only one wire.

The cava filters may be created with a relatively loose weave allowingthe blood to flow freely. In an exemplary embodiment, it is preferablethat the distal end of the cava filters is not completely closed. SeeFIGS. 6-8. Instead, the bent ends of the wires (FIG. 7 and FIG. 8 showsmall closed loops, but bends may also be used) or the coupled ends ofthe wires (FIG. 6) are arranged to form a relatively round opening witha diameter of about 2 to 5 mm. The size of the wires that may be usedfor forming the cava filters other than the barbless stent filter(discussed below) ranges from between about 0.009 inches and about 0.013inches, but is most typically about 0.011 inches. The size of the wiresthat may be used for forming the barbless stent filter ranges frombetween about 0.008 inches and about 0.015 inches, but is most typicallyabout 0.011 inches.

As with the stents of the present invention, the angle between thecrossing wires of the cava filters is preferably obtuse. Similarly, atthe proximal end (e.g., FIG. 6) of the filter, either a loop or bend maybe formed by bending the wires as above described. When such closedstructures are made at the distal end of the filters, the angle formedmay be acute as shown in FIGS. 7, 8 and 9A. At the distal (e.g., FIG. 6)or proximal end (e.g., FIG. 7 and FIG. 8) of the cava filters, the wireends may be coupled together to form closed structures as abovedescribed.

Advantageously, the portions of the wires forming the closed structuresmay be bent outwardly into multiple barbs to anchor the filter, whenlocated at the proximal ends of the cava filters (e.g., FIG. 7 and FIG.8). As used herein, “barbs” are portions of the ends of the wires thatmay be used to form the cava filter. By carefully selecting the size,orientation and shape of the barbs, they may penetrate the vessel wallin order to better anchor the filter during use, but they may also bedisengaged from the vessel wall as the filter is being retrieved butprior to the filter being withdrawn such that the possibility of causingany damage to the vessel wall is minimal. As illustrated in FIG. 59,barb 74 of closed structure 4 is penetrating vessel wall 73 at an angle75 that is acute. Although angle 75 may be obtuse, the inventors havefound that barb 74 generally anchors the filters more securely whenangle 75 is acute rather than when it is obtuse. Beginning at side 77 ofvessel wall 73 and extending to the end of barb 74, barb 74 may be about1 to 2 mm long. As shown, wire end 7 may be oriented at an angle that isroughly perpendicular to the angle of barb 74 such that barb 74 isprevented from more deeply penetrating vessel wall 73. Another exampleof suitably shaped barbs may also be found on the RECOVERY filter, whichis commercially available from C. R. Bard, Inc. (www.crbard.com; MurrayHill, N.J., 800 367-2273).

The cava filters of the present invention may be formed by plain weaveusing the methods described above for forming the stents. Of course, anappropriately shaped template may be chosen. Shapes for the cava filtersinclude a cone (FIG. 6 and FIG. 7), a dome (FIG. 8), an hourglass shape(FIG. 9), and the shape of the barbless stent filter (FIG. 51). The cavafilters may also be heated as the stents are, and may be allowed to coolas the stents are. Additionally, in an exemplary embodiment, as with thetapered stent, the filters may be woven on a cylindrical template,heated and allowed to cool, then the body formed may be remodeled andthen reheated on another template. In an exemplary embodiment of thehourglass filter, for example, the body formed by weaving may be heatedand cooled, and then may be remodeled into the shape of an hourglass bynarrowing the central portion using a material suitable for reheatingsuch as copper/brass wire; then the hourglass shaped body may bereheated.

In an exemplary embodiment of the cava filters of the present invention,it may be preferable to flare and compress the woven structure near theproximal end of a conical or dome shape filter or near both the proximaland distal ends of an hourglass filter, forming a cylindrical portionwith a relatively tight weave (see portions 140 in FIG. 6, FIG. 7 andFIG. 9) prior to heating. The diameter over this portion may bevirtually constant. In an exemplary embodiment, this portion may beformed using the above-described method of heating and cooling a filterthat may not possess the desired portion, reconstraining or remodelingthe filter to achieve the desired shape of the portion, securing thegiven portion of the filter in the desired shape and heating and coolingthe constrained filter again.

In an exemplary embodiment, this constant-diameter portion and/or theflared ends of the cava filters may be advantageously used foranchoring. By achieving strong contact between the filter and the vesselwall, the filter's intraluminal position can be further secured. Theexpansile force of the cava filter (which depends partly on the numberand size of the wires which are used for making the structure) may bechosen so as to ensure such strong contact. The use of the flaredportions as well as the suitable barbs may virtually eliminate thepossibility of migration.

The cava filters of the present invention will be further described inmore detail below by the way of specific examples.

a. Conical Filter—FIGS. 6 and 7

With reference to the illustrative embodiments shown in FIGS. 6 and 7,there are shown conical filters for insertion and delivery into vascularanatomical structures. The conical filters include a plurality of wireswhich may be arranged in a plain weave as described above so as todefine an elastically deformable body 150. As shown in FIGS. 6 and 7,body 150 has a wide and/or flared proximal end 142 and a distal end 144.The diameter of body 150 is larger at proximal end 142 than at distalend 144. The diameter of body 150 decreases from proximal end 142 todistal end 144. Distal end 144 may be formed in such a way that almostno opening is left through which fluid might flow. As discussed above,however, in an exemplary embodiment, it is preferable to leave arelatively round opening with a diameter of about 2 to 5 mm.

b. Dome Filter—FIG. 8

With reference to the illustrative embodiment shown in FIG. 8, there isshown a dome filter for insertion and delivery into a vascularanatomical structure. The dome filter includes a plurality of wireswhich may be arranged in a plain weave as described above so as todefine an elastically deformable body 152. As shown in FIG. 8, body 152like body 150, may have a wide and/or flared proximal end 142 and adistal end 144. The diameter of body 150 is larger at proximal end 142than at distal end 144. The diameter of body 150 decreases from proximalend 142 to distal end 144. The degree of the decrease in the diameterfrom the proximal to the distal end is not as steep as in the conicalversion, however. As a result, body 152 more resembles a hemisphere thana cone. Because of its hemispherical shape, the dome filter may occupyless longitudinal space within the cava than other filters.

c. Hourglass Filter—FIG. 9

With reference to the illustrative embodiment shown in FIG. 9, there isshown an hourglass filter for insertion and delivery into a vascularanatomical structure. The hourglass filter includes a plurality of wireswhich may be arranged in a plain weave as described above so as todefine an elastically deformable body 154. As shown in FIG. 9, body 154has two conical or dome portions 146 bridged by a narrow portion 148.The diameter of distal and proximal ends 144 and 142 is larger than thediameter of portion 148. In an exemplary embodiment, distal end 144 ispreferably not equipped with barbs. The closed structures of proximalend 142 may be bent outwardly to form barbs. The lumen size of narrowportion 148 may be selected so as not to close the lumen of the filtercompletely. The hourglass filter shown in FIG. 9 has multiple filtratinglevels; in an exemplary embodiment there may be almost no difference inthe filtrating capacity between the filtrating capacity of the center ofthe filter and the filtrating capacity of the periphery of the filterbecause the blood may be filtered by the peripheral weave of both theproximal and distal portions 146. FIG. 10 shows an hourglass filterplaced in the IVC.

d. Barbless Stent Filter—FIG. 51

With reference to the illustrative embodiment shown in FIG. 51, there isshown a barbless stent filter for insertion and delivery into a vascularanatomical structure. The barbless stent filter includes a plurality ofwires which may be arranged in a plain weave as described above so as todefine body 400, which, like all the other bodies in this disclosure, issuitable for implantation into an anatomical structure. As shown in FIG.51, body 400 may consist of base 402, mid-portion 404, and dome 406.

Base 402 may be made as a straight stent (as described above) with agiven diameter. As a result, base 402 may serve to anchor the filterwithin a vessel and may not participate in blood filtration. In anotherembodiment of this filter, base 402 may also be made with a changingdiameter. For example, its lumen may be slightly tapered from base 402to mid-portion 404. The mesh tightness of base 402 may approach themaximum-achievable tightness (i.e., 180°). Accordingly, the radial forceof the anchoring portion (base 402) will increase as the mesh tightnessincreases.

Additionally, by carefully selecting the diameter of base 402, body 400may be configured to retain its position within a vessel without the useof barbs. As a result, the task of carefully selecting the size,orientation, and shape of the barbs that could otherwise be used suchthat those barbs may be elevated from the caval wall so as to greatlyreduce the possibility of damaging the vessel wall during resheathing(as a result of repositioning or removing the filter) may be eliminated.In an exemplary embodiment of the barbless stent filter, the diameter ofbase 402 may be 26-30 mm, which represents operable diameters inninety-five percent of the population, which has an inferior vena cavaof less than 28 mm in diameter. In an exemplary embodiment of thebarbless stent filter, the length of base 402 may not exceed 10-15 mm.

As shown in FIG. 51, mid-portion 404 of the barbless stent filterincludes struts 408, which are formed of twisted wires 5. Struts 408 arearranged so as to be oriented in substantially parallel relationshipwith the axis of the portion or segment of the vessel in which they aredelivered or released. Struts 408 may serve to further stabilize thebarbless stent filter within the vessel or non-vascular structure intowhich the filter is delivered. For example, in the embodiment of thebarbless stent filter shown in FIG. 52, struts 408 may be slightly bentor bowed outward so as to increase the frictional forces between thedelivered filter and the vessel wall. As a result, the self-anchoringcapability of the filter may be increased. In an exemplary embodiment ofthe barbless stent filter, the length of mid-portion 404 may be about5-10 mm.

Turning to the third portion of the barbless stent filter, as shown inFIG. 51, the mesh tightness of dome 406 may be loose. In one embodimentof this filter, the top portion of the dome may be equipped with hook410 to facilitate the removal of the filter. In such an embodiment, hook410 may be small and made of metal or any other suitable material, andmay be firmly and permanently attached to wires 5. Similarly, althoughnot illustrated, with the benefit of the present disclosure one ofordinary skill in the art will understand that hook 410 may also beprovided on the proximal ends of the other cava filters disclosedherein. Additionally, the hooks on these filters may be used during thepossible repositioning or retrieval of such filters in the same way asmay be used on the barbless stent filter, described below in greaterdetail.

In another embodiment, the barbless filter may be provided with twofiltration levels. As shown in FIG. 53, such a filter is composed of twodomes 406 (arranged inversely), a mid-portion 404 having a tight stentmesh similar to the mesh of base 402 in the embodiments in FIGS. 51 and52, and two, intermediate segments 412 having short, struts 408 betweendomes 406 and mid-portion 404. In one version of this embodiment, boththe top and bottom portions of the domes may be equipped with hook 410to facilitate the removal of the filter. Alternatively, either the topor bottom may be equipped with hook 410.

The end of the barbless stent filters located proximate hook 410depicted in FIGS. 51-53 may be positioned so as to achieve a variety ofconfigurations. For example, the end may be stretched such that theshape of domes 406 is closer to a triangle than the shape depicted inFIGS. 51-53, or the end may be compressed.

The shape of the barbless stent filters may be formed using the methodsdescribed above for forming the stents and other cava filters. Forexample, the barbless stent filter may be woven on an appropriatelyshaped template. Then the filter and template may be heated and cooledas above described. Alternatively, the barbless stent filter may bewoven on a cylindrical template and heated and allowed to cool.Alternatively, prior to heating and cooling, certain portions such asthe mid-portion and dome may be reconstrained or remodeled, and theremodeled portion of the filter may then be secured and heated andcooled again.

e. Biodegradable Filters

As indicated above, all of the filters of the present invention(including the BI filter discussed below) may be formed with filamentsmade of biodegradable material so as to form self-expanding,self-anchoring, bioabsorbable, biodegradable filters that may, inaddition to functioning as filters, function as drug or nutrientdelivery systems as a result of the material used. In one embodiment,the biodegradable filters of the present invention may be provided withreinforcement wires as above described.

The factors that may be considered in choosing the materials from whichto form the biodegradable stents, the materials themselves, the methodsof forming the biodegradable stents and reinforcing the stents withwires, apply to the filters as well. In addition, one may also considerthe following: the flow conditions of the vessel into the biodegradablefilters are placed (e.g., high flow conditions within the vena cava), tobetter ensure that the material and weave of the filter are chosen suchthat the filter may anchor properly within the vessel; the rate ofdegradation of the chosen material as well as the time at which thedegradation will begin so that if the filter is used as a temporaryfilter (as described below), the entrapped thrombi may be attended tobefore the filter degrades to an extent that the entrapped thrombi couldbe released back into the bloodstream.

Any of the cava filter embodiments disclosed herein may be made fromboth wires 5, (wires 5 may be made from any of the materials describedabove, such as nitinol) and appropriate biodegradable filaments 540.Although the barbless stent filter is described below in this regard, itis by way of example only, and with the benefit of the presentdisclosure, one having skill in the art will understand that wires 5 andbiodegradable filaments 540 may be connected to each other ashereinafter described for the other embodiments of the cava filtersdisclosed herein.

Base 402 may be formed from wires 5, while dome 406 may be formed fromfilaments 504, which may be formed from an appropriate biodegradablematerial, such as one described above in greater detail. In thisembodiment, the transition between the two materials may be created inmid-portion 404. The connection between each nitinol wire and thecorresponding filament may be made by using any suitable means such asglue, heat, by wrapping the filament around the wire, or any combinationof thereof. After biodegradation of dome 406 has taken place, base 402may, like a self-expanding stent, be left behind in the body.

f. Single-Wire Embodiment Filter

As with the occluders, the single wire embodiment may also be utilizedas a structure for filtering thrombi within a vessel. The single wireembodiment filters may be formed in the same manner as the single wireembodiment occluders are formed. Moreover, the single wire embodimentfilters are simply the single wire embodiment occluders without anythrombogenic agents attached to the body of the single wire embodimentfilters. In this regard, FIG. 60 illustrates body 700 of a single wireembodiment filter. The body has first segment 704 and second segment 706separated by a bend in the wire that is in the form of closed loop 6.The body is provided with multiple collars 702, which hide multipleloop-defining locations where the segments are positioned adjacent toeach other. (Adjacent has the same meaning with respect to the singlewire embodiment filters as it has with respect to the single wireembodiment occluders.) The segments 704 and 706 extend between theloop-defining locations so as to form multiple loops 710, which aredesignated in FIG. 60 by the segments that outline them. Anotherembodiment of the present single wire filters is illustrated in FIG. 15.As illustrated in both FIGS. 60 and 15, loops 710 of bodies 700 possesscompressed shapes.

Delivery System of the Cava Filters

Version 1 shown in FIG. 3 may be used as the delivery system for thecava filters (including each of the versions described above) accordingto the present invention.

Delivery of the Cava Filters

Prior to insertion and delivery, a cava filter in the form of a body150, 152, 154, 400 (or biodegradable versions thereof), or body 700 maybe manually secured to tubes 22 and 40 of version 1 as above described.The cava filter may then be stretched as described above so as to reducethe diameter of its largest portion by an amount appropriate such thatthe filter may be inserted into a vessel (preferably with the use of anaccess sheath), and may pass through the lumen of the vessel as thefilter is being positioned prior to being delivered into the vessel.FIG. 28 shows a filter secured to a delivery system in a completelystretched state.

In one embodiment of the method for delivering the cava filters of thepresent invention, a hollow covering such as a guiding sheath may beplaced over the filter secured to the delivery system to prevent contactbetween the filter and the vessel wall as the filter is inserted andpositioned for delivery. In another embodiment, a short, introducersheath with a check-flo adapter may be used at the access site toprevent contact between the filter and the vessel into which the filtermay be inserted during insertion of the filter; in such an embodimentthe introducer sheath may or may not be used to cover the filter beyondthe access site of the vessel.

The cava filters of the present invention may be stretched completely onthe delivery system, reducing their diameters as much as possible, asshown in FIG. 28, for example. In one embodiment, after being secured tothe delivery system and stretched to some extent, a filter may bedelivered into the inferior vena cava (“IVC”). In such an embodiment,the filter may be inserted into either the right or the left femoralvein, allowing for a femoral approach. In such an embodiment, the filtermay be inserted into the internal jugular vein, allowing for a jugularapproach. In such an embodiment, a filter and delivery system with arelatively small profile, such as 7-F, for example, may be inserted intoa peripheral vein (pl. antecubital vein), allowing for a peripheralapproach, if the system is sufficiently flexible. As discussed abovewith regard to the delivery of the stents, the construction of thedelivery system enables one to use a guidewire in the lumen of tube 22for delivery of the filter, in an exemplary embodiment of the presentinvention. It is to be understood however, that a guidewire may not beutilized at times.

Each of the cava filters may be delivered into place in the mannerdescribed above with regard to the delivery of the stents using version1 (see, Delivery of the Stents). All the advantages described above withregard to repositionability, etc., including the advantage of being ableto compress the filter being delivered and achieve as tight a mesh inthe cylindrical portions thereof (such as base 402 of the barbless stentfilter) as possible, apply equally to the delivery of the cava filters.Further, in instances in which one of the present cava filters isdelivered in the IVC, for example, the elasticity of the IVC wall allowsthe operator to achieve an even tighter mesh than the mesh originallycreated after the annealing process. That is, a filter configured withan angle a of 155° may be compressed during delivery until angle a is170°, and, if the filter is properly oversized, the elasticity of theIVC wall may maintain angle a at very close or equal to 170°. Theability of the present delivery system to achieve this scenario isespecially advantageous when the filter is created without barbs so asto maintain its position within the vessel into which it may bedelivered by virtue of the radial force between the filter and thevessel wall.

The weave of the present filters (including those discussed below) isespecially suitable to advantageously allow mechanical thrombus-suctionto remove the entrapped clots without the risk of dislodging the thrombiand allowing them to travel to the systemic and pulmonary circulation.In so doing, an adequately sized catheter with a large lumen may beinserted into the filter's lumen and used to suck the thrombi out. Thismethod may be used in combination with thrombolysis.

a. Non-Permanent Cava Filter Applications

All of the woven cava filters, particularly the conical, dome, andbarbless stent filters, may be used in temporary applications. A basicneed exists to remove entrapped thrombi safely and successfully beforeremoval of a temporary filter. The emboli entrapped by any kind oftemporary filter can be dealt with in a variety of ways, such asthrombolysis, placement of a permanent filter, or allowing small thrombito embolize to the lungs. The woven structure of the cava filters of thepresent invention seems favorable to prevent escape of the entrappedclots during thrombolysis. As a result, there is probably no need toplace another filter above the woven temporary filter. This wouldotherwise be impossible if the temporary filter is delivered from ajugular approach. The temporary applications of the cava filters includeboth temporary and retrievable filter designs.

Temporary filters may be attached to a catheter or sheath, a tube or aguidewire that may project from the insertion site (e.g., using a hubwith a cap which is sutured to the skin for fixation), so as to allowfor easy removal of the filter. Retrievable filters are permanentfilters that have a potential to be removed.

Both the temporary and the retrievable filters may be delivered via ajugular approach. It is to be understood, however, that these filtersmay also be delivered via a femoral or antecubital approach.

In one embodiment, a temporary filter may be created by manuallysecuring a cava filter to two tubes in the manner described above. Theouter tube to which the proximal end of the filter may be secured maycomprise a catheter or sheath, or it may comprise a tube such as tube 40described above. Being a low profile design, the temporary filtertypically does not require an outer tube larger than 7 French.

After properly positioning the temporary filter, the distal end of thetemporary filter may be released using the above described method. Ifthe temporary filter is no longer in the proper position, the filter maybe withdrawn as shown in FIGS. 27A and B. FIGS. 27A and B illustratetube 71 (which may, for example, be any suitably-sized catheter orsheath) being advanced over a filter such that barbs 74 of the filterthat penetrate vessel wall 73 are disengaged from vessel wall 73 as tube71 is advanced and the filter is held stationary. A monofilament (notshown) may be threaded through one or more of the bends or closed loopsdefining the proximal end of the filter. Both ends of the monofilamentmay be positioned in an easily accessible location (such as exterior ofthe patient). The operator can then advance tube 71 over the ends of themonofilament (as described below with respect to monofilament loop 172depicted in FIG. 12) while holding the monofilament steady to disengagebarbs 74 from vessel wall 73 prior to the withdrawal of the filter.

After releasing the distal end of the filter, the holes in thesuperelastic tubing through which the securing wire or wires werethreaded may be used for injection of some urokinase or tissueplasminogen activator (TPA) to lyse entrapped thrombi within the mesh.FIG. 26 depicts the situation in which the distal end of the filter hasbeen released. As shown in FIG. 26, openings 27 may be provided in tube22, in addition to proximal and distal holes 24 and 26, through whichurokinase or TPA may as just described. FIG. 26 also depicts introducersheath or catheter 99, which may be utilized in conjunction with thepresent delivery system to facilitate the insertion of the deliverysystem, including tubes 22 and 40, into the patient. (Note that pushbutton lock/release mechanism 200 shown in FIG. 25 as connecting tube 40and 22 is not depicted in FIG. 26.) Introducer catheter 99 may beattached to end fitting 204, as shown in FIG. 26, with a Luerconnection. FIG. 26 also illustrates that multiple securing wires 46 maybe utilized for securing the proximal end of the filter to tube 40. Inthis regard, although not shown, it will be understood to those of skillin the art, with the benefit of this disclosure, that securing wires 46may be controlled by creating openings in tube 40 near the proximal endof tube 40 and threading the proximal ends of securing wires 46 throughthose holes. In this way, the proximal end of the filter or other devicemay be released by pulling the proximal ends of securing wires 46.Tightening screw 205 may be provided on the end of the side arm of endfitting 204, as shown in FIG. 26, for fixing the relative positions ofsecuring wires 30 (not shown). Additionally, although not shown, it willbe understood to those of skill in the art, with the benefit of thisdisclosure, that a tightening screw may be provided on the end of endfitting 204 for fixing or securing the relative position of anyguidewires that are utilized as well.

In this embodiment of the invention, there may be no need to applybarbs/tabs at the distal end of the temporary filter. For example, thebarbless stent filter, by nature, will not be equipped with barbs.However, such barbs or tabs may be supplied as shown in FIG. 27A to theother filters. The proximal end of the outer tube may be secured to theskin using surgical sutures. When the filter is to be removed, thetemporary filter may be withdrawn into a catheter/sheath (such as tube71) and the device may be withdrawn from the body.

An additional manner in utilizing the barbless stent filter as atemporary filter exists that does not involve leaving an outer tube inthe body. In one embodiment, hook 410 may be used as a tool for removinga temporary filter. At the appropriate time, a foreign body snare, suchas the Amplatz Goose Neck snare (Microvena Corp., White Bear Lake,Minn.) may be used to grasp hook 410 and retract the filter into anappropriately sized thin-walled sheath for removal from the body. Thesnared end of the filter may be held stationary and anappropriately-sized sheath (approximately 2-French sizes larger than thedelivery system) may be advanced over the shaft of the foreign bodysnare to capture the filter.

For the retrievable filter, the distal end may be equipped withbarbs/tabs. At the proximal end of the retrievable filter, amonofilament loop is threaded through the small closed loops (or bends)created from the bent wires such that the small closed loops becomeinterconnected by the monofilament loop (see, e.g., FIG. 12); thus,pulling on the monofilament loop will result in drawing the small closedloops together thus reducing the diameter of the stent at the proximalend. The retrievable filter may be secured to the same delivery systemused for delivery of the temporary filter in the same way.

Delivery may also be carried out in the same way. In an exemplaryembodiment, the filter may be delivered from a right jugular approach.It is to be understood that if the delivery system is small enough, anantecubital approach may be acceptable, especially for a short timefiltration. It is to be understood that delivery from a femoral approachmay require the filter to be positioned inversely. After delivery of theretrievable filter from a jugular approach, for example, the deliverysystem may be removed and, only the monofilament loop may be left withinthe vasculature. The very proximal end of the loop may be attached tothe skin as above described. In this form, the retrievable filter may beused as a temporary filter. Both the flared base with the tighter meshand the barbs/tabs may serve to anchor the retrievable filter within thecava. In the case of the barbless stent filter, base 402 may serve thefunction of the flared base of the other filters, which may or may notbe provided with barbs or tabs. If it is necessary to convert thetemporary filter into a permanent one, the monofilament loop may besevered and removed from the small closed loops of the filter as well asfrom the body.

If a decision is made to remove a retrievable filter, a short metalstraightener may be advanced over the proximal end of the monofilamentloop. A short introducer sheath may then be inserted in the access veinover the straightener. Through the introducer, an adequate size sheathmay be advanced to the distal end of the filter. Stretching themonofilament loop, the sheath may be advanced over the filter. As aresult, the barbs/tabs, if utilized, will be retracted from the cavalwall, and the filter's removal can be achieved without causing injury tothe vessel wall.

The time period for leaving a temporary filter in a patient will varyfrom case to case, but, generally, temporary filters may be left inplace for no more than about two to three weeks. Leaving them in placefor a longer period of time may result in the formation of a neointimallayer on the temporary filter, which would impede its removal. Toincrease the period of time during which these filters may be left inthe body without being embedded into the neointimal layer, the filtersmay be coated with some biologically active materials (e.g.,cytostatics, fibroblast growth factor [FGF-1] with heparin, Taxol, etc.)or the metal of the filter may be rendered β-particle-emitting producinga low-rate radiation at the site of the filter placement (Fischell,1996).

The main advantage of the retrievable filter is that if the conversionfrom temporary to permanent filtration is necessary, there is no need toremove the temporary filter and deploy a permanent one. Both versionsare suitable for intraluminal thrombolysis both from a jugular or afemoral approach or possibly an antecubital approach.

The retrievable filter provides additional advantages in that they areeasily retrievable, they possess equal filtering capacity in the centerand at the periphery of the cava, they provide safe thrombolysis, theyare self-centering and self-anchoring, and unless hook 410 is utilizedin conjunction with the barbless stent filter, it is unnecessary to usea foreign-body retrieval device which might involve lengthymanipulations. However, it is to be understood that, in someembodiments, small tabs may be coupled to the ends of the filters of thepresent invention for facilitating the removal of the filter with aforeign body retrieval device.

The cava filters of the present invention provide the advantage ofimproved filtration. The extended coverage of the filtering level comeswith an improved thrombus capturing capacity of the cava filters. Thepresence of a thrombus in a traditional conical filter decreases thecapture rate for a second embolus (Jaeger, 1998). The succeedingthrombus will not be able to get into the apex of the cone and has ahigher chance of passing through the filter (Kraimps, 1992). The flowvelocity, and therefore, the hydrodynamic force are increased at thestenotic site of the filter. Because conical filters predominantlycapture thrombi in the apex of the cone, the site of increased velocityis located at the periphery of the filter. As long as the diameter ofthe thrombi is smaller than or equal to that of the stenotic opening,the locally increased velocity and hydrodynamic force will push thethrombi through the filter periphery.

Using the cava filters of the present invention, the thrombi will beprimarily captured by the distal end of the conical and dome filters andby the dome of the barbless stent filter; in the case of the hourglassfilter, the first filtration level is the narrow portion of the proximalend of the filter. Any subsequent emboli will be diverted to theperiphery of the cava where the filter has approximately the samefiltration capacity as in the center of the filter.

The filtration capacity of a filter can be estimated by looking at itfrom the top or below. The wires/mesh arrangement in the projectedcross-section of the filtered segment of the IVC gives a good estimateabout the “coverage” of the IVC by the filter. For example, FIG. 29depicts a projected cross section of one of the present hourglassfilters taken across the middle portion of the filter. In the case ofthe hourglass filter, the blood is primarily filtered by the proximalhalf of the filter, similar to the case using the dome or conicalfilter. The blood which is going proximally alongside the caval wallwill be filtered the peripheral mesh of both the proximal and the distal“dome”. As a result, as in the case of the barbless stent filter, thereis virtually no difference in filtration capacity of the filter in thecenter and at the periphery of the vessel. Additionally, with respect toeach of the filters, the immediate opening and symmetric arrangement ofthe bases of the filters serves to self-center them and prevent themfrom being tilted. Some filter designs (especially theGreenfield-filter) are sensitive to intraluminal tilting, whichnegatively affects their filtration capability.

The flexibility of the mesh of the cava filters, as is the case with allthe woven intravascular devices of the present invention, makes itpossible to advance the delivery system through tortuous vessels. Thisfeature together with the small size of the delivery system enables oneto deliver these filters via every possible access site of the body.Further, as with all the intravascular devices of the present invention,the plain weave of the cava filters allows for the production of onecoherent element, which does not possess any kind of joints.

The cava filters according to the present invention may possess(depending on the material used to form the wires thereof) anon-ferromagnetic character making them, as well as stents formedtherefrom, MRI compatible.

The cava filters of the present invention are also suitable forintravascular thrombolysis. After placement of any kind of filteringdevice, the development of caval thrombosis/occlusion frequently occurs(Crochet, 1993). In acute cases, a possible therapeutic option is torecanalize the IVC by pharmaco-mechanical thrombolysis. Doing so in thepresence of the currently available filters poses a high risk ofdeveloping pulmonary emboli, because large fragments of the IVC thrombuscan break off and be carried away in an uncontrolled way afterurokinase/TPA treatment. One of the acceptable options in that situationis to place another filter above the thrombosed filter to avoidpulmonary embolism due to thrombolysis. Unlike other designs, the cavafilters according to the present invention may offer the possibility ofa safe and successful thrombolysis without the need for the placement oftwo filters.

Bi-Iliac Tube Filter

The wires of the BI filter according to the present invention may bemade of the same materials as the wires of the stents. The same numberof wires may be used in forming the BI filter as are used to form thestents. However, in an exemplary embodiment, less wires are preferablyused for the BI filter than for the stents. It is to be understood thatalthough only 4 wires appear in FIGS. 11-13, 2 more wires are not shown.The BI filter may be created with a relatively loose mesh allowing theblood to flow freely. The size of the wires that may be used for formingthe BI filter ranges from between about 0.008 inches and about 0.011inches, but is most typically about 0.009 inches.

The BI filter according to the present invention may be formed using theabove described methods for forming the stents. Of course, anappropriately shaped template may be chosen. In weaving body 160 of theBI filter, as shown in FIGS. 11-13, the angle a between the crossingwires is preferably obtuse. It is to be understood that angle a may alsobe less than or equal to 90°. End 164 may have a plurality of closedstructures which may be small closed loops 166 (FIGS. 12 and 13) orbends 168 (FIG. 11), like the above stents and filters. The angles ofthose closed structures may be similar to the angles for the closedstructures of the stents as above described. The wire ends at 162 ofbody 160 may be coupled together in the manner above described.

Body 160 of the BI filter may also be heated as the stents are, and maybe allowed to cool as the stents are.

In one embodiment, the mid-portion of the BI filter may be constructedwith a larger diameter than that of the ends which are used forfixation. This may be achieved in a variety of ways using the remodelingmethods above described. For example, one may weave a straight stentwith a caliber useful for filtration (larger lumen). Then, smallercaliber ends may be formed by remodeling the filter on a smaller calibertemplate. In such a case, the weave of the filtering level will belooser than those of the legs. In another embodiment, the weave of thefiltering level may be tighter than those of the legs by weaving the BIfilter is on a template sized for the legs, and then remodeling thefilter by ballooning the mid-portion of the filter outward. Manyvariations in shape are thus possible.

The BI filter of the present invention may be stretched completely onthe delivery system, reducing its diameter as much as possible. It maybe delivered in that stretched state into the inferior vena cava(“IVC”). It is to be understood that it may also be delivered into theIVC in a state that is not completely stretched. The filter may beinserted from either femoral vein and placed into both iliac veinsforming an inverse U-shape bridging over the confluence of these veins.Unlike traditional IVC filters, the filtration according to the presentinvention will substantially take place through the cephalad surface 163of the weave at about the mid-portion of body 160 located at thejunction of the iliac veins, as shown in FIG. 11.

The BI filter is suitable for temporary filtration. In this embodimentof the present invention shown in FIG. 12, the coupled wire ends formthe distal end of the filter, while the multiple small closed loops 166located proximally are connected by a monofilament loop 172 as describedabove and shown in FIGS. 12 and 13. FIGS. 12 and 13 illustrate Bi-filter160 delivered within left iliac vein 157 and right iliac vein 158,beneath the inferior vena cava 159. Using a contralateral approach, thefilter may be inserted from either femoral vein and its front end may bepositioned into the contralateral iliac vein. After delivery of thefilter, the monofilament loop may be led outside the body and secured tothe skin. When there is no further need for the filter, it may bewithdrawn by pulling it back by the monofilament loop through anadvanced sheath.

In another possible embodiment of this invention shown in FIG. 13, aflexible, superelastic wire or microtubing 174 made from nitinol (orsimilar superelastic/shape memory material described above) is ledthrough the lumen of the BI filter. The distal end of the nitinolwire/microtubing is attached or coupled to one twisted wire-end 170 ofthe filter by any suitable means, including soldering, point welding,wrapping of fibers, and the like. The proximal end of thewire/microtubing may be attached to the skin (along with themonofilament loop). When the BI filter is being withdrawn, thewire/microtubing may be held steadily, while the monofilament loop ispulled. As a result, the BI filter will be partially stretchedfacilitating the filter's removal. The BI filter may also be removed inthe fashion described above for removing the temporary filter.

As discussed above, given the design of the BI-filter, one maycatheterize the lumen of the filter and, using an adequate sizecatheter, thrombus-suction may be easily performed before filterremoval.

Delivery System of the BI Filter

Version 1 shown in FIG. 3 may be used as the delivery system for the BIfilter (including a biodegradable version) according to the presentinvention.

Delivery of the BI Filter

A preferably preformed guiding catheter or a guiding sheath (Balkinsheath-type) (FIG. 3) may be used for insertion of the delivery systemfor the embodiments discussed above. The BI filter may be secured to andstretched out on the surface of the delivery system in a mannerdescribed above, and may be delivered from the ipsilateral femoral/iliacvein through the caval junction into the contralateral iliac vein. Asdiscussed above with regard to the delivery of the stents, theconstruction of the delivery system enables one to use a guidewire inthe lumen of tube 22 for delivery of the filter, which is preferable inan exemplary embodiment of the present invention. It is to be understoodhowever, that a guidewire may not be utilized if a preformed sheath isin place.

The BI filter may be delivered into place in the manner described abovewith regard to the delivery of the stents using version 1. All theadvantages described above with regard to repositionability, etc., applyequally to the delivery of the BI filter. In an exemplary embodiment ofthe delivery method for the BI filter, the distal end of the BI filtermay be released first.

Advantageously, the BI filter according to the present invention mayoffer the possibility of a safe and successful thrombolysis, like thecava filters above discussed.

All of the methods and apparatus disclosed and claimed herein can bemade and executed without undue experimentation in light of the presentdisclosure. While the methods and apparatus of the present inventionhave been described in terms of illustrative embodiments, it will beapparent to those of skill in the art that variations may be applied toapparatus and in the steps or in the sequence of steps of the methodsdescribed herein without departing from the concept, spirit and scope ofthe invention. More specifically, it will be apparent that certainagents which are both chemically and physiologically related may besubstituted for the agents described herein while the same or similarresults would be achieved. All such similar substitutes andmodifications apparent to those skilled in the art are deemed to bewithin the spirit, scope and concept of the invention as defined by theappended claims.

REFERENCES

The following references, to the extent that they provide exemplaryprocedural or other details supplementary to those set forth herein, arespecifically incorporated herein by reference.

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1. A medical stent comprising: a plurality of geometric cells defining astent, the stent having first and second opposed open ends; and aplurality of wire strands woven to form a plurality of crossed regionsdefining said geometric cells; wherein each wire strand has strand endsand the strand ends are disposed at said second end of said stent. 2.The stent of claim 1, wherein the wire stands are bent to define saidfirst end of said stent.
 3. The stent of claim 1, wherein the wirestrands at least one of said crossed regions cross at an angle, whichangle decreases when the stent is radially compressed.
 4. The stent ofclaim 1, wherein the wire strands at least one of said crossed regionscross at an angle, which angle increases when the stent is radiallyexpanded.
 5. The stent of claim 4, wherein the angle is increasinglyobtuse as the stent is radially expanded.
 6. The stent of claim 4, wherethe angle is from about 70° to about 100°.
 7. The stent of claim 4,where the angle is from about 20° to about 160°.
 8. The stent of claim4, where the angle is from about 90° to less than about 180°.
 9. Thestent of claim 4, where the angle is from about 140° to about 160°. 10.The stent of claim 4, where the angle is from greater than about 0° toabout 45°.
 11. The stent of claim 4, where the angle is less than about90°.
 12. The stent of claim 4, where the angle is greater than or equalto about 90°.
 13. The stent of claim 4, where the angle is acute. 14.The stent of claim 4, where the angle is obtuse.
 15. The stent of claim4, wherein the stent foreshortens when the stent is radially expanded.16. The stent of claim 1, wherein said wire strands are nitinol wirestrands.
 17. The stent of claim 1, wherein said crossed regions comprisecrossed regions without having said strands being helically wrappedthereat.
 18. The stent of claim 1, wherein the wire strands at thecrossing points are not twisted.
 19. The stent of claim 1, wherein thegeometric cells have a diamond shape.
 20. The stent of claim 1, whereineach strand has a diameter from about 0.004 inches to about 0.008inches.
 21. The stent of claim 1, wherein each strand has a diameterfrom about 0.003 inches to about 0.015 inches.
 22. The stent of claim 1,wherein each strand has a diameter from about 0.003 inches to about0.006 inches.
 23. The stent of claim 1, wherein each strand has adiameter from about 0.005 inches to about 0.012 inches.
 24. The stent ofclaim 1, wherein each strand has a diameter from about 0.006 inches toabout 0.012 inches.
 25. The stent of claim 1, wherein each strand has adiameter from about 0.006 inches to about 0.009 inches.
 26. The stent ofclaim 1, wherein each strand has a diameter from about 0.009 inches toabout 0.013 inches.
 27. The stent of claim 1, wherein each strand has adiameter from about 0.008 inches to about 0.015 inches.
 28. The stent ofclaim 1, wherein each strand has a diameter of about 0.007 inches. 29.The stent of claim 1, wherein each strand has a diameter of about 0.009inches.
 30. The stent of claim 1, wherein each strand has a diameter ofabout 0.011 inches.
 31. The stent of claim 1, wherein pairs of thestrands at said second end are attached to one and the other.
 32. Thestent of claim 1, wherein the strands at said second end are secured toone and the other.
 33. The stent of claim 1, wherein the strands at saidsecond end are helically twisted.
 34. The stent of claim 1, wherein thestent is coated with silicone.
 35. The stent of claim 1, furthercomprising a covering.
 36. A medical stent comprising: a plurality ofgeometric cells defining a stent, the stent having first and secondopposed open ends; and a plurality of wire strands woven to form aplurality of crossed regions defining said geometric cells; wherein thewire stands are bent to define said first end of said stent and furtherwherein each wire strand has strand ends and the strand ends aredisposed at said second end of said stent.
 37. The stent of claim 36,wherein said crossed regions comprise crossed regions without havingsaid strands being helically wrapped thereat.
 38. The stent of claim 36,wherein the wire strands at the crossing points are not twisted.
 39. Thestent of claim 36, wherein the geometric cells have a diamond shape. 40.The stent of claim 36, wherein the wire strands at least one of saidcrossed regions cross at an angle, which angle decreases when the stentis radially compressed.
 41. The stent of claim 36, wherein the wirestrands at least one of said crossed regions cross at an angle, whichangle increases when the stent is radially expanded.
 42. The stent ofclaim 41, wherein the angle is increasingly obtuse as the stent isradially expanded.
 43. The stent of claim 41, where the angle is fromabout 70° to about 100°.
 44. The stent of claim 41, where the angle isfrom about 20° to about 160°.
 45. The stent of claim 44, wherein thestent foreshortens when the stent is radially expanded.
 46. The stent ofclaim 41, where the angle is from about 90° to less than about 180°. 47.The stent of claim 41, where the angle is from about 140° to about 160°.48. The stent of claim 41, where the angle is from greater than about 0°to about 45°.
 49. The stent of claim 41, where the angle is less thanabout 90°.
 50. The stent of claim 41, where the angle is greater than orequal to about 90°.
 51. The stent of claim 41, where the angle is acute.52. The stent of claim 41, where the angle is obtuse.
 53. The stent ofclaim 36, wherein said wire strands are nitinol wire strands.
 54. Thestent of claim 36, wherein the strands at said second end are helicallytwisted.
 55. A method of making a medical stent, comprising: providing aplurality of wire strands, each strand having strand ends; bending thewire strands to form a first end of the stent; and diagonally weavingthe wires to produce a plurality crossed regions defining a plurality ofgeometric cells; wherein said strand ends form a second end of thestent.
 56. The method of claim 55, wherein the step of weaving comprisesforming the plurality of crossing points without having the wire strandshelically wrapped thereat.
 57. The method of claim 55, wherein the stepof weaving comprises forming the plurality of crossing points withouthaving the wire strands twisted thereat.
 58. The method of claim 55,wherein the wire strands at least one of said crossed regions cross atan angle, which angle decreases when the stent is radially compressed.59. The method of claim 55, wherein the wire strands at least one ofsaid crossed regions cross at an angle, which angle increases when thestent is radially expanded.
 60. The method of claim 59, wherein theangle is increasingly obtuse as the stent is radially expanded.
 61. Themethod of claim 59, where the angle is from about 70° to about 100°. 62.The method of claim 59, where the angle is from about 20° to about 160°.63. The method of claim 62, wherein the stent foreshortens when thestent is radially expanded.
 64. The method of claim 59, where the angleis from about 90° to less than about 180°.
 65. The method of claim 59,where the angle is from about 1400 to about 160°.
 66. The method ofclaim 59, where the angle is from greater than about 0° to about 45°.67. The method of claim 59, where the angle is less than about 90°. 68.The method of claim 59, where the angle is greater than or equal toabout 90°.
 69. The method of claim 59, where the angle is acute.
 70. Themethod of claim 59, where the angle is obtuse.
 71. The method of claim55, wherein said wire strands are nitinol wire strands.
 72. The methodof claim 55, wherein the geometric cells have a diamond shape.
 73. Themethod of claim 55, wherein each strand has a diameter from bout 0.004inches to about 0.008 inches.
 74. The method of claim 55, wherein eachstrand has a diameter from about 0.003 inches to about 0.015 inches. 75.The method of claim 55, wherein each strand has a diameter from about0.003 inches to about 0.006 inches.
 76. The method of claim 55, whereineach strand has a diameter from about 0.005 inches to about 0.012inches.
 77. The method of claim 55, wherein each strand has a diameterfrom about 0.006 inches to about 0.012 inches.
 78. The method of claim55, wherein each strand has a diameter from about 0.006 inches to about0.009 inches.
 79. The method of claim 55, wherein each strand has adiameter from about 0.009 inches to about 0.013 inches.
 80. The methodof claim 55, wherein each strand has a diameter from about 0.008 inchesto about 0.015 inches.
 81. The method of claim 55, wherein each strandhas a diameter of about 0.007 inches.
 82. The method of claim 55,wherein each strand has a diameter of about 0.009 inches.
 83. The methodof claim 55, wherein each strand has a diameter of about 0.011 inches.84. The method of claim 55, wherein pairs of the strands at said secondend are attached to one and the other.
 85. The method of claim 55,wherein the strands at said second end are secured to one and the other.86. The method of claim 55, further comprising: coating the stent withsilicone.
 87. The method of claim 55, further comprising: providing acovering to the stent.
 88. A medical stent comprising: a plurality ofgeometric cells defining a stent, the stent having first and secondopposed open ends; and a plurality of wire strands woven to form aplurality of crossed regions defining said geometric cells; wherein thewire stands are bent to define said first end of said stent and furtherwherein each wire strand has strand ends and the strand ends arehelically twisted and disposed at said second end of said stent.
 89. Amedical stent comprising: a plurality of geometric cells defining astent, the stent having first and second opposed open ends; and aplurality of wire strands woven to form a plurality of crossed regionsdefining said geometric cells, the crossed regions having at least oneangle which increases when the stent is radially expanded; wherein thewire stands are bent to define said first end of said stent and furtherwherein each wire strand has strand ends and the strand ends aredisposed at said second end of said stent.
 90. The stent of claim 89,where the angle is from about 70° to about 100°.
 91. The stent of claim89, where the angle is from about 20° to about 160°.
 92. The stent ofclaim 89, where the angle is from about 90° to less than about 180°. 93.The stent of claim 89, where the angle is from about 140° to about 160°.94. The stent of claim 89, where the angle is from greater than about 0°to about 45°.
 95. The stent of claim 89, where the angle is less thanabout 90°.
 96. The stent of claim 89, where the angle is greater than orequal to about 90°.
 97. The stent of claim 89, where the angle is acute.98. The stent of claim 89, where the angle is obtuse.
 99. The stent ofclaim 89, wherein the stent foreshortens when the stent is radiallyexpanded.
 100. A medical stent comprising: a plurality of geometriccells defining a stent, the stent having first and second opposed openends; and a plurality of wire strands woven to form a plurality ofcrossed regions defining said geometric cells, the crossed regionshaving at least one obtuse angle which increases when the stent isradially expanded; wherein the wire stands are bent to define said firstend of said stent and further wherein each wire strand has strand endsand the strand ends are disposed at said second end of said stent. 101.A stent comprising: a plurality of wires arranged in a weave to definean elastically deformable body having a proximal end and a distal end;wherein the wires cross each other to form a plurality of angles, andwherein ends of the plurality of wires are located proximate to theproximal end of the body.
 102. The stent of claim 101, wherein at leastone of the angles is obtuse.
 103. The stent of claim 102, wherein thevalue of the obtuse angle is configured to increase when the body isaxially compressed.
 104. The stent of claim 102, wherein the value ofthe obtuse angle is configured to increase when the body is radiallyexpanded.
 105. The stent of claim 101, wherein the body is configured toforeshorten when the body is radially expanded.
 106. The stent of claim101, wherein the weave comprises a plain weave.
 107. The stent of claim101, wherein the weave comprises at least some of the wires beingtwisted to each other where at least some of the wires cross.
 108. Thestent of claim 101, wherein at least some of the wires are coupled atthe proximal end.
 109. The stent of claim 108, wherein at least some ofthe wires are twisted at the proximal end.
 110. The stent of claim 101,wherein at least some of the wires comprise a memory shape alloy. 111.The stent of claim 110, wherein the memory shape alloy comprisesnitinol.
 112. The stent of claim 101, further comprising a coatingcomprising silicone.
 113. A method of forming a stent, the methodcomprising weaving a plurality of wires to define an elasticallydeformable body having a proximal end and a distal end; wherein weavingcomprises crossing the wires at a plurality of angles, and wherein endsof the plurality of wires are located proximate to the proximal end ofthe body.
 114. The method of claim 113, wherein weaving comprisesbending the wires to form the distal end of the body.
 115. The method ofclaim 113, wherein weaving comprises crossing the wires without twistingthe wires.
 116. The method of claim 113, wherein weaving comprisestwisting the wires where at least some of the wires cross.
 117. Themethod of claim 113, further comprising coupling the ends of the wiresat the proximal end.
 118. The method of claim 117, wherein coupling theends of the wires comprises twisting the wires at the proximal end. 119.The method of claim 117, wherein coupling the ends of the wirescomprises soldering the wires at the proximal end.
 120. The method ofclaim 113, further comprising coating the body with silicone.